In various parts of the article Electricity, we have described a great variety of instruments for ascertaining the presence of electricity, and measuring its quantity or proportion.
But there are several instruments of this kind that have not been described in that article; and as they are well deserving a place in this work, either from the ingenuity of their construction, the reputation of their inventors, or the intrinsic value of the instruments themselves, we shall give an account of them here.
Fig. 1. Plate CC. is a geometrical representation of Mr Cavallo's improved atmospheric electroscope, of half its real size. The principal part of this instrument is a glass tube CDMN, cemented at the bottom into the wooden piece AB, by which part the instrument is to be held when used for the atmosphere; and it also serves to screw the instrument into its wooden case ABO, fig. 2, when it is not to be used. The upper part of the tube CDMN, is shaped tapering to a smaller extremity, which is entirely covered with sealing-wax, melted by heat, and not dissolved in spirits. Into this tapering part a small tube is cemented, the lower extremity G of which being also covered with sealing-wax, projects a short way within the tube CDMN. Into this smaller tube a wire is cemented, which with its lower extremity touches the flat piece of ivory H, fastened to the tube by means of cork; the upper extremity of the wire projects about a quarter of an inch above the tube, and screws into the brass cap EF, which cap is open at the bottom, and serves to defend the waxed part of the instrument from the rain, &c. In fig. 3, a section of this brass cap is represented, in order to show its internal shape, and the manner in which it is screwed to the wire, projecting above the tube L. The small tube L, and the upper extremity of the large tube CDMN, appear like one continued piece, on account of the sealing-wax, which covers them both. The conical corks P of this electroscope, which by their repulsion show the electricity, &c., are as small as can conveniently be made, and they are suspended by exceedingly fine silver wires. These wires are shaped in a ring at the top, by which they hang very loosely on the flat piece of ivory H, which has two holes for that purpose. By this method of suspension, which is applicable to every sort of electroscope, the friction is lessened almost to nothing, and thence the instrument is sensible of a very small degree of electricity. IM, and KN, are two narrow slips of tin-foil, stuck to the inside of the glass CDMN, and communicating with the wooden bottom AB; they serve to convey off that electricity, which, when the corks touch the glass, is communicated to it, and being accumulated, might disturb the free motion of the corks.
In regard to its use, this instrument may serve to observe the artificial, as well as the atmospherical electricity. When it is to be used for artificial electricity, this electroscope is set upon a table or other convenient support; then it is electrified by touching the brass cap EF with an electrified body, which electricity will sometimes be preserved for more than an hour. Mr Cavallo had one of these electrometers which would remain electrical for more than twelve hours, though in a room without a fire. If in an electrified state, any electrified substance be brought near the cap EF, the corks of the electroscope, by their converging, or by increasing their divergence, will show the species of that body's electricity.
It is necessary to remark, that to communicate any electricity to this electroscope, by means of an excited electric, e.g., a piece of sealing-wax, (which we suppose is always negatively electrified), is not very readily done in the usual manner, on account of the cap EF being well rounded, and free from points or sharp edges. By the approach of the wax, the electroscope will be caused to diverge; but as soon as the wax is removed, the wires immediately collapse. The best method to electrify it, is to bring the excited wax so near the cap, that one or both the corks may touch the side of the bottle CDMN; after which, they will soon collapse and appear unelectrified: if now the wax be moved, they will again diverge, and remain electrified positively.
When this instrument is to be used to try the electricity of the fogs, the air, the clouds, &c., the observer is to do nothing more than to unscrew it from its case, and, holding it by the bottom AB, to present it to the open Electrometer, open air, a little above his head, so that he may conveniently see the corks P, which will immediately diverge if there be any sufficient quantity of electricity; whose nature, i.e., whether positive or negative, may be ascertained by bringing an excited piece of sealing-wax, or other electric, towards the brass cap EF.
It is perhaps unnecessary to remark, that this observation must be made in an open place, as the roads out of town, the fields, the top of a house, &c.
The principal advantages of this electrometer, as stated by Mr Cavallo, are as follows:
1. The smallness of its size. Mr Cavallo made one so small, that its case, which was of brass, measured only three inches and a half in length, and nine-tenths of an inch in diameter, and yet it acted perfectly well.
2. Its being always ready for experiments, without fear of entangling the threads, or having an equivocal result by the sluggishness of its motion.
3. Its not being disturbed by wind or rain.
4. Its great sensibility; and,
5. Its keeping the communicated electricity longer than any other electrometer.
II. Sauflure's Electrometer. M. de Saufure's electrometer, with which he made the observations on atmospheric electricity, that have been related in the second chapter of Part V. of the article Electricity, and represented at fig. 4, is much the same with that of Mr Cavallo above described. The following are the most material circumstances in which they differ: First, the fine wires, by which the balls are suspended, should not be long enough to reach the tin-foil which is pasted on the inside of the glass, because the electricity, when strong, will cause them to touch this tin-foil twice consecutively, and thus deprive them in a moment of their electricity. To prevent this defect, and yet give them a sufficient degree of motion, it is necessary to use larger glasses than those that are generally applied to Mr Cavallo's electrometer; two or three inches in diameter will be found to answer the purpose very well. But as it is necessary to carry off the electricity which may be communicated to the inside of the glass, and thus be confounded with that which belongs to those substances that are under examination; four pieces of tin-foil should be pasted on the inside of the glass; the balls should not be more than one-twentieth of an inch diameter, suspended by silver wires, moving freely in holes nicely rounded. The bottom of the electrometer should be of metal; for this renders it more easy to deprive it of any acquired electricity, by touching the bottom and top at the same time.
In order to collect a great quantity of electricity from the air, the electrometer is furnished with a pointed wire, 15 inches or two feet long, which unscrews in three or four pieces, to render the instrument more portable; see fig. 4. When it rains or snows, the small parasol, fig. 5, is to be screwed on the top of the instrument, as by this its insulation is preserved, notwithstanding the rain.
This instrument indicates not only the electricity of fogs, but also of serene weather, and enables us to discover the kind of electricity which reigns in the atmosphere; and to a certain degree to form an estimate of its quantity, and that under two different points of view, the degree of intensity, and the distance from the earth at which it first begins to be sensible.
A conductor raised for the purpose of making observation on atmospherical electricity will be found to exhibit signs of electricity, only when the electric fluid is more or less condensed in the air, than in the earth. Though the air resists the passage of the electric fluid, it is not absolutely impermeable to it; it suffers it to pass gradually, and generally with more ease in proportion as its mass or thickness is less. It is therefore interesting to discover at what height it is necessary to be elevated, in order to find a sensible difference between the electricity of the earth, and that of the air. A very sensible difference may be generally discovered by this instrument, at the distance of four or five feet from the ground; sometimes it may be seen if the instrument is placed even on the ground; while at others, it must be raised seven or more feet before the balls will open; sometimes, though seldom, this height is not sufficient. This distance is generally greatest when the electricity is strongest, though necessarily modified by a variety of circumstances, some of which are known, as the degree of dryness or humidity of the air, and others are unknown.
The degree of intensity, at a given height, may be discovered thus; raise the electrometer, and judge by the divisions which are placed on the edge of it, the degree of their divergence. To find the relation between this degree of divergence, and the force of the electricity, M. de Saufure took the following method: As he could not with certainty double or triple a given quantity of electricity; yet as a given force may be reduced one half, a fourth or eighth, &c., by dividing between two equal and similar bodies, the electricity contained in one; he took two of his unarmed electrometers, which were as similar as possible, and electrified one of them, so that the balls separated precisely six lines; he then touched the top thereof by the top of that which was not electrified; in an instant the electricity was equally divided between them, as was evident by the divergence of the balls, which was four lines in each; consequently a diminution of half the density had only lessened the divergence one-third. One of these electrometers was then deprived of its electricity, and was afterwards brought in contact with the other, as before; the remaining electricity divided itself again between them, and the balls fell from four to twenty-eight lines, nearly in the same proportion as before; in the third operation they fell to nineteen; in the fourth to one, where he was obliged to stop, as there was not now sufficient force in the fluid to pass from one electrometer to the other, and distribute itself uniformly between them. The same experiment, repeated several times, gave very nearly the same results. Negative electricity decreased also in the same proportion as the positive. The following table may therefore be considered as giving a general, though not exact idea of the increase in force, which corresponds to different degrees of divergence in the balls; it is only calculated to every fourth of a line; the force of electricity is always expressed by whole numbers, as it would be ridiculous to put a greater degree of exactness in the numbers than is to be found in the experiments which form the bases of the calculation. Those who are desirous to carry this measure of the electric force further, may do it by having similar electrometers constructed, but made upon a larger scale, and with heavier balls, which would only separate one line, with the degree of electricity that makes the smaller ones diverge five lines; these would consequently measure a force 1024 times greater than that which forms the unity of the preceding table; and thus by degrees we may be enabled to discover the ratio of the strongest discharge of a great battery, or perhaps even of thunder itself, to that of a piece of amber, which only attracts a bit of straw or any other light substance.
In order to observe the electricity of the atmosphere with this instrument, we must first bring the electric fluid contained in the electrometer to the same degree of density with that at the surface of the earth; this is easily done by letting the bottom and top touch the ground at the same time; then raise the point, keeping the bottom still in contact with the ground, from whence it may be lifted up in a vertical position till the balls are level with the eye.
The second circumstance is to render the divergence of the balls, which is occasioned by the electricity of the air, permanent. This is effected by touching the top of the electrometer with the finger; but here the acquired electricity becomes contrary to that of the body by which they are electrified. Let us suppose, for example, that the electrometer is at five feet from the ground, and the balls diverging; touch the top of the electrometer with the finger, and the balls will close; but they will again open, if the electrometer is withdrawn from the influence of the electricity of the air, by being brought nearer the ground, or into the house. M. Saufler only employed this method when the electricity was so weak that he could not perceive any until the electrometer was raised considerably above his eye; as in this case he could not perceive the divergence of the balls, he always endeavoured to obtain a permanent electricity in the foregoing manner.
The following example will render the use of the foregoing observations more familiar. Choose an open situation free from trees and houses, screw the conductor on the top of the electrometer, lay hold of it by its base, and place it so that the base and conductor may touch the ground at the same time; then elevate it to the height of the eye, and observe the quantity of lines, or fourths of a line, that the balls have diverged; now lower it till the balls almost touch each other, and observe at what distance the top of the conductor is from the ground; and this is the height from the ground at which the electricity of the air begins to be sensible. If the electricity of the air is sufficiently strong to make the balls diverge when it stands upon the ground, one of the lengths of the electrometer must be unfurled from it. If the balls, however, still diverge, the other parts of the conductor should also be unfurled, and you may mark down, that the electricity is sensible at zero, or on the surface of the earth. If, on the contrary, the electricity is so weak, as not to cause the balls to diverge when they are even with the eye, and consequently when the conductor is two feet higher, or seven feet from the ground, you should then raise it a foot higher; while it is thus elevated, touch the top with the other hand; when this hand is taken away, lower the electrometer, and if it is electrified, you may say the electricity is sensible at eight feet; if it is not, raise it as high as the arm can reach, and repeat the same operation; if any electricity is found, write down electricity sensible at nine feet; if not, mark 0, or no electricity relative to this instrument, and this mode of employing it; for signs of electricity may still be obtained, by throwing a metallic ball 50 or 60 feet into the air, which is at the same time connected with the electrometer by a metallic thread.
One advantage of this instrument is, that it will often exhibit signs of electricity when none can be obtained from a conductor of 100 feet in height, because it can more easily be preserved from humidity, &c., which will destroy the insulation of the large conductors.
This electrometer may be used instead of the condenser of M. Volta, by only placing it on a piece of oiled silk, somewhat larger than the base of the instrument; but in this case, it is the base, and not the top of the instrument, which must be brought into contact with the substance whose electricity is to be explored.
It is easy to discover also by this instrument, the electricity of any substance, as of cloths, hair of different animals, &c. For this purpose, it must be held by the base, and the substance rubbed briskly (only once) by the ball of the electrometer; the kind of electricity may be ascertained in the usual manner. It is proper, however, to observe here, that as the top of the electrometer acts in this case as an insulated rubber, the electricity it acquires is always contrary to that of the rubbed body.
III. Cudell's Electrometer, is thus described by the author, as translated in Nicholson's Journal.
Fig. 6. In a glass tube A, 18 or 20 inches long, Fig. 6, is inclosed another shorter tube X, sealed at both ends. This tube contains a graduated scale: one of the ends of these two tubes is cemented in a handle of turned wood. Electrometer wood, C, by which it is held in the hand; the other end is closed by a brass cap, D; the distance between the extremities of the small tube and that of the large one is filled with red wax, B, B; on the cap D is screwed at pleasure, either a ring E, or a brass hook F. The ring is used for applying the instrument to the ball of a conductor, and the hook when it is hung to a ring: on the cap D is a brass stem G, terminating by a knob. This item is bended, and the extremity of its knob must be directly beneath the line with which the graduated scale of the small tube commences.
Round the large tube is a brass ring H, half of which extends to the length of twelve or fifteen lines in the form of a half tube P, applied against the sides of the tube. This gutter serves to mark the degrees, by sliding along the graduated scale by means of a button beneath I. On the ring H is fixed one of the small electrometers invented by Saufure, K, K, which is furnished with a stem V, on which item is fixed at pleasure either a point L, or a ball M, of the same size as that which terminates the stem G, opposite which it is placed. The extremity of this point or ball must be placed immediately over the extremity of the half tube or scale P, and horizontally to the centre of the ball, which terminates the stem G.
At the top of Saufure's electrometer is a small ring N, which serves to connect it with the chain Z when required.
To explain the use of this instrument by a single experiment, charge a Leyden jar, till the spontaneous overflowing announces it to be saturated. Then place the ring E on the knob of this bottle, and cause the electrometer of Saufure, armed with its point, to slide towards it. Observe the degree at which the divergence of the thread stream commences, and at that instant suppress the point, and adapt in its place the ball M. Continue to advance the electrometer of Saufure till the electric pressure of the atmosphere in the jar causes the threads to diverge; again observe the degrees, replace the point L, and close the shutters of the room; then continue to advance the electrometer till the luminous point appears, which again affords new degrees. Lastly, replace the ball M, and fix the chain Z to the small ring N; cause it to communicate with the exterior coating of the jar, and advance the electrometer till the explosion takes place. Then comparing the different degrees, we may ascertain the comparative difference between the respective methods.
As soon as these relative proportions have been once accurately ascertained by attentive observations, one of those methods alone will be sufficient for measuring the intensity of electricity; and, in fact, if the body intended to be submitted to examination be little charged with the electric fluid, the diverging of the threads, by means of the point, will fix the limits of the electric atmosphere: if it be more, the pressure of the atmosphere on the ball M, which is substituted for the point, will indicate this quantity. In short, if the body be loaded with a considerable mass of electric matter, it will be shown by the luminous point. If a Leyden jar, instead of being positively, is negatively electrified, the point indicates it at the same time that it measures the electric atmosphere, for instead of a luminous point, a star will be observed upon the ball of the jar, and another at the end of the point.
Let us now apply this electrometer to useful observations.
In order to connect the idea of a determinate quantity of fluid to each degree of the electrometer, it is necessary to compare these degrees with the known quantities. Suppose for instance we have a jar, the coating of which is six inches square; electrify it till a spontaneous discharge takes place, and remark, by means of Henley's electrometer, at what degree this discharge is effected. Again, electrify the jar, till it is nearly saturated, and measuring with this electrometer, observe, that the luminous point appears for instance at two degrees; then say, that when the electrometer, applied to an electrified body, marks two degrees, the body contains six inches square of electricity. Repeat this experiment with a plate of glass, the coating of which is seven, eight, ten, or twelve square inches, and we may form a scale of proportion, which is of the greatest utility in accurate experiments.
"In endeavouring to ascertain some of these propositions," says M. Cadet, "I have made an observation which has convinced me of the utility of my electrometer in discovering the capacity of electric apparatus. Having taken a jar from an electric battery, I electrified it, and measured it with a point which I passed along a string of silk; on observing the distance at which the luminous point appeared, I joined this jar to another of the same size, and imagined that by doubling the quantity of matter, the measure I had taken would also be doubled; on the contrary, however, the latter measure was not more than about one-third of the former: I then added a third bottle; and still obtained nearly the same result; whence the following proposition appears to be established; namely, that the extent of the electric atmosphere is in an inverse ratio to the quantity of fluid accumulated. Another observation which I have several times made, on measuring the electric atmosphere of a conductor, is, that the limits of this atmosphere form an elliptic figure around the body, nearly similar to that represented at fig. 7.
"This doubtless arises from the electrified body suspended in a chamber, being nearer to the earth than the ceiling; but it would be a curious experiment to measure it at an equal distance from every attracting body, in order to observe whether the fluid has not really a tendency to descend towards the earth, rather than in any other direction. It is my intention to repeat this experiment, as I consider it of great importance to ascertain whether electricity gravitates towards the globe.
"From these first attempts, I conceive my electrometer would be well adapted for measuring the absolute capacity of Leyden jars, and also their capacity with regard to their size, or to the quality of the glass of which they are constructed; for the latter, by its greater or less density, absorbs a greater or less quantity of fluid."
IV. Layton's Electrometer. This is a simplified improvement on Brooke's steelyard electrometer, and should have been described when that instrument was mentioned, instead of Mr Adams's; but it did not occur to us till after that sheet was printed. The following account is given of this electrometer, in a letter from Mr. Lawson to the editor of the Philosophical Magazine.
"Some time ago it struck me that some additions to Brooke's electrometer might be made, so as to fit it for a good discharging electrometer to measure the repulsion between two balls (of a certain size) in grains, and also effect the discharge of a battery at the same time. The instrument known by the name of Cuthbertson's discharging electrometer, (See Electricity, No. 203.) was at that time the best, and indeed the only instrument for discharging batteries or jars by its own action, then made; but I think this will be found, in the essentials, and in the theory and use, a more perfect instrument."
On the basis (fig. 8.) is fixed the glass pillar G, supporting the hollow brass ball B. It is a light graduated brass tube, divided (from the weight W towards the ball B) into thirty parts, representing grains. W is a sliding weight. L, a light brass ball screwed to the end of the tube I. On the other end of which tube adjusts the heavy counterbalance ball C, the tube I and its two balls being suspended at their common centre of gravity by a silk line in the centre of the ball B, the mechanism of which is shown in fig. 9. The brass ball F is stationary, and of the same size as the ball L; and is fixed by, and adjusts close to, the ball L, or at any lower station between that and the ring r. The brass tube to which the ball A is fixed is divided into inches halves, and quarters; (a more minute division is unnecessary and improper). The divisions begin, or the line o is marked on the said tube at the ring r, when the three balls A, L, F, are close together. The ring r serves as an index, as the divisions pass in succession into the brass tube P on lowering the ball A. The hook H is screwed into the base of P. The quadrant, or Henley's electrometer, Q, is supported in a long brass stem, to keep it out of the atmosphere of the lower part of the instrument. Fig. 9 shows the internal construction of the ball B, fig. 8. In the first place the ball screws in half, horizontally. The light tube I passes through the ball, and is suspended nearly in the centre of it by some silk twist, r, which small silk twist is fixed into the eye of the adjusting wire, a, part of which wire is filed square and goes through the square hole h. The nut n screws on a, and serves to adjust the light tube I vertically. The light plates PP are of copper, and move freely on the wire ww somewhat like a hinge, and rest on the copper wires CC, serving to make the direct communication between the inside and out of the battery or jar. NN are notches serving to let the tube I descend when the discharge is made. Into the tube Z the glass pillar is ground. Note, that at the bottom of the notch N is a piece of brass filled with a Y, and so placed as to keep the centres of the balls L and F, fig. 8, under each other when they come close together.
"When the instrument is adjusted, which is done by placing the weight W, fig. 8, at o on the line of grains, and then removing or unremoving the counterbalance ball C, till the tube I rises slowly into its horizontal position; then set the ball A at the distance from the ball L that you choose, and the weight W placed at the division or number of grains that you wish the repulsive power of the electricity to arrive at before the discharge is made: this being done, connect the battery or jar electrometer with the ball B, by means of the wire y, the end of which goes into B at the hole X, and should stand at right angles to B, the ball of y resting on the battery: then connect the outside of the battery or jar with the hook H. As the battery charges, the electrometer Q continues to rise; and when it is so highly charged that the repulsive power between the balls L and F is equal to the number of grains at which the weight W was placed, the ball L will descend, and deliver the charge of the battery to the ball A. The substance or thing through which the shock is intended to be passed, must form part of the communication between the hook H and the outside of the battery or jar."
V. Haughton's Electrometer. Fig. 10 contains a representation of this electrometer, and the different parts of which it consists. OP is a board of dry mahogany, twelve inches in length and four in breadth, which serves as a stand for the instrument. In this board are fastened two malleable glass pillars, M and N, which support the two brass caps or rings GG, with the two forks of tempered steel KK screwed into them. The two rings GG are well covered with varnish.
In the ring is fastened a brass rod, which terminates in a ball E of the same metal, and an inch in diameter. The length of the rod and ball together is four inches and a half.
A very delicate beam AB, the arms of which are of unequal length, moves on a sharp triangular axis (a knife edge) of well tempered steel, on the fork K of the pillar M. It is seventeen inches in length, and so constructed that the short arm forms a third, and the long one two-thirds of the whole beam. The short arm of brass furnished with the ball B, exactly of the same size as the ball E, is divided into forty-five parts equivalent to grains. The long arm A is of glass covered with copal varnish, and ends in an ivory ball A, into which is fitted an ivory hook R, destined to support the ivory scale H. In order to render the inflation more complete, this scale is suspended by three hairs.
A very delicate beam CD, eleven inches in length, moves on an axis like the former, on the pillar N, though not here shown. This beam is proportioned in the same manner, one arm being a third and the other two-thirds of the whole length. The long arm of brass is furnished at the end with a ball D, and divided into thirty parts corresponding to grains. The short arm of glass terminates in a long roundish plate C, covered with copal varnish. The steel forks are shown by the sections of the two brass caps FF, as are also the two knife edges L, L. By these caps the escape of the electric matter is partly prevented.
A brass ring Q, capable of being moved along the short arm of the upper beam AB, shows by means of marks determined by trial and cut out on the beam, the number of grains which must be placed in the small scale to restore the equilibrium of the beam, at each distance of the ring Q from the point of suspension.
On the long arm CD of the lower beam there is also a moveable ring S, which, like the ring Q, shows in grains, by its distance from the point of suspension, the power requisite to overcome the preponderance of LD in regard to LC.
The power necessary for this purpose will be found, if the shell H, which weighs exactly fourteen grains, be- suffered to sink down on the glass plate C, and the ring s be pushed forwards till both the arms of the beam are in equilibrium. The part of the beam on which the ring s has moved, is divided into fourteen parts, so that o marks the place where the ring s must stand when the beam, in its free state, is in equilibrium; and 14 stands at the place where the ring s again restores a perfect equilibrium when the shell H is laid on the glass plate C. Each of these parts, which are divided into quarters, indicates a grain. The lower divisions of the scale will be found with more accuracy, if quarters of a grain be put, in succession, into the shell H (after it has been laid on the plate C), and the ring s be moved be- tween each quarter of a grain until the perfect equili- brium be restored. This place on the beam is then to be marked, and you may continue in this manner until the 30th part of a grain be given. Both scales, for the sake of distinctness, are divided only so low as quarters of a grain; though the instrument is so delicate, and must absolutely be so, that 1/20th of a grain is sufficient to destroy the equilibrium.
The two glass pillars M and N, together with the steel forks affixed to them, are so fitted into the stand that both the beams lie parallel to each other as well as to the rod GE. In this position of the beams AB, the balls B and E are just in contact. The smallest glass pillar N is of such a height that the ball of the beam CD stands at the distance of exactly four lines from the ring G, and cannot move without touching the latter. The small shell H is suspended in such a manner that there is a distance of exactly two lines between it and the shell C. In each of the brass rings GG is a small hole, that the instrument may be connected with the two sides of an electric jar. I is a brass wire, with a hollow bit of ivory, a, defined to support the beam CD, which is necessarily preponderate at D, in order to prevent oscillation between the discharges to be examined by the instrument.
It may be readily comprehended that, when the beam AB has moved, A must pass over twice the space that B does; and that in the beam CD, the case is the same in regard to C and D. If AB be therefore con- nected with the external, and CD with the internal side of a battery, but in such a manner that the instrument is at a sufficient distance beyond the electric atmosphere; and if the battery be charged, the repulsive effect of the electric power will oblige the ball B to separate from the ball E; the shell L must therefore naturally sink down with double velocity, so that when the ball B rises a line, the shell H must sink two; when it reaches this depth it will touch the shell C, and the lat- ter, by the power excited in it, will be obliged to sink, by which D must naturally again ascend in a double proportion to the sinking of C; so that when C has fallen two lines, D must have ascended four, and D that moment touches the ring s by which the two sides of the battery are connected with each other, and dis- charges the battery.
But as the attractive electric power between unlike atmospheres, under like circumstances, is at least as strong as its repulsive power between like atmospheres, it would thence follow, that the electric power, instead of repelling the ball B from the ball E, would rather attract D, and by its contact with G, promote the dif- charging; by which the instrument would fail of its object, and be subjected to the temperature of the at- mosphere like all other electrometers; and, besides this, the electric power could no longer be determined by weight. To obviate this inconvenience, the instrument, in all electrical experiments, must be applied in such a manner that the power with which the ball D is attract- ed by AB may exceed in strength the power required to repel the ball B from the ball E. For this purpose the ring s must always be removed two divisions farther on CD, towards D, than the ring Q is shifted on AB towards B. If, for example, an electric force were re- quired equal to eight grains, according to this electro- meter, the ring Q must be removed to the place where 8 stands, and the ring s to the place marked 10. The repulsive power will then naturally repel the balls B and E before G is in a condition to attract the ball D, as a power of two grains would be necessary for this pur- pose, besides that of the eight already in action. The shell H with its weight of fourteen grains, will easily overcome the preponderance of LD or LC, as it amounts only to ten grains, and therefore nothing exists that can impede the discharging.
When the ring r, according to the required power, is removed so far towards D, that the shell H is not able by its weight to destroy the preponderance of LD in regard to LC, the active power of the shell H must be so far increased by the addition of weights, that it can act with a preponderance of four grains on the plate C. If, for example, an electric power of 14 grains be required, the ring r must be removed to 16, by which LD rests upon a, with a preponderance of 16 grains in regard to LC. Now, to make H act on the plate C with a preponderance of four grains, it must be increased to 20 grains, that is, fix grains weight more must be added, as it weighs only 14; which fix grains are again laid upon LB; and therefore the ring Q is shifted to 20, as the strength of the repulsive power is pointed out by 14 grains.
If an electric power of 25 grains be required, the ring s must be removed to 27, and the weight of 17 grains be put into the shell H, in order to produce a preponderance of four grains in regard to s. These 17 grains are added to the required power of 25 grains, and the ring Q is pushed to 42, &c. In this manner the repulsive power always acts before the attractive power can.
It may be readily perceived that the faults and in- conveniences common to all the electrometers hitherto employed, and which have been already mentioned, cannot take place here; because the discharging is per- formed by immediate connection between the positive and negative electricity in the instrument itself, without any external means being employed.
One of the most essential advantages of this instru- ment is, the certainty with which the same result may be expected when the experiment is repeated. From the same degree of electric power, whatever be the temperature of the atmosphere, it will always be neces- sary to commence the separation of the two balls B and E from each other, the quantity of coated glass and the distance of the ring Q from the axis L being the same.
Another no less important advantage of this instru- ment is, that in an experiment where the same electric power, power, often repeated, is necessary to ascertain the result with accuracy; such, for example, as the charging a battery through acids, water, &c.; the same degree of precaution is not necessary as is indispensably to be taken in any other electrometer, as the person who puts the machine in motion has nothing to do but to count how often the electrometer discharges itself; and the instrument may be inclosed in a glass case, or prevented in any other manner from external contact, or any other circumstances which might render the experiment uncertain.
"I flatter myself (says M. Hauch), that the simplicity of the construction of this instrument, the facility with which it may be made at a very small expense, and the certainty that two instruments, prepared according to the same scale, with a like quantity of coated glass, must exactly correspond with each other; but above all, that the certainty and accuracy by which experiments may be made with it, and by these means be accurately described, are advantages which will not be found united in any of the electrometers hitherto invented."
We shall close this account of electrometers with describing the construction and use of M. Coulomb's electrometer, or, as he calls it, Electrical Balance.
ABCD (fig. 11.) represents a glass cylinder, twelve inches in diameter and the same in height, covered by a glass plate fitted to it by a projecting fillet on the under surface. This cover is pierced with two round holes one inch and three-fourths in diameter. One of them is in the centre, and receives the lower end of the glass tube f, of twenty-four inches height, which is fixed in the hole with a cement made of sealing-wax, or other electric substance. The top of this tube receives the brass collar H, (fig. 12. No. 3,) bored truly cylindrical with a small shoulder, which rests on the top of the tube. This collar is fastened with cement, and receives the hollow cylinder φ (fig. 12. No. 2,), to which is joined the circular plate a, divided on the edge into 360 degrees. It is also pierced with a round hole G in the centre, which receives the cylindrical pin i (fig. 12. No. 1,) having a milled head b, and furnished with an index i o, whose point is bent down so as to mark the divisions on the circle a b. This pin turns freely in the hole G, and the cylinder φ moves steadily in the collar H. To the lower end of the centre pin is fastened a little pincer, q, formed like the end of a port-crayon, and tightened by the ring r, so as to hold fast the suspension wire, the lower end of which is grasped by a similar pincer, P o (fig. 13.) tightened by the ring φ. The lower end φ o is cylindrical, and is of such a weight, as to draw the wire perfectly straight, but without any risk of breaking it. It may be made equal to half of the weight that will just break it.
This pincer is enlarged at C, and pierced with a hole, which tightly receives the arm g C q of the electrometer. This arm is eight inches long; and consists of a dry silk thread, or a flender straw completely dried, and dipped in melted lac or fine sealing-wax, and held perpendicularly before a clear fire, till it become a flender cylinder of about one-tenth of an inch in diameter. This occupies six of the eight inches, from g to q; the remaining two inches consist of a fine thread of the lac or sealing-wax, as it drains off in forming the arm. At a, is a ball of pith or fine cork, one-fourth or one-half of an inch in diameter, made very smooth, and gilded. It is balanced by a vertical circle of paper g, of large dimensions, made stiff with varnish. The refraction of the air to this plane soon checks the oscillations of the arm.
The whole instrument is seen in its place in fig. 11., where the arm hangs horizontally about the middle of the height of the great cylinder. In its oscillations the ball a moves round in a circle, whose centre is in the axis of the whole instrument. Its situation is indicated by a graduated circle z o q, drawn on a slip of paper, and made to adhere to the glass by varnish. The electrified body whose action is to be observed, is another small ball of cork t, also gilt, or a brass ball well polished. This is carried by a stalk of lac m φ, inclosing a dry silk thread. This stalk is grasped by a clamp of cleat deal, or any similar contrivance, which is made to lie firm on the glass cover. When this ball is let down through the hole m, it stands so as to touch the ball a on the arm, when that ball is opposite to o on the graduated circle.
In order to electrify the ball t, we are to employ the inflating handle, fig. 14, which is a slender stick Fig. 14. of sealing-wax or lac, holding a metal wire that carries a small polished metallic ball. This is to be touched with some electrified body, such as the prime conductor of a machine, the knob of a jar, &c. This electrified ball is to be introduced cautiously into the hole m, and the ball t is to be touched with it. The ball a is immediately repelled to a distance, twisting the suspension wire, till the force of twist exerted by the wire balances the mutual repulsion of the balls t and a.
This is the process for examining the law of electric action. When it is desired to examine the action of different bodies in different states, another apparatus is wanted. This is represented by the piece c A d (fig. 15.) consisting of a plug of sealing-wax A, fitting tightly into the hole m, and pierced by the wire c d, hooked at c, to receive a wire to connect it occasionally with an electrified body, and having below a polished metal ball d.
The instrument is fitted for observation in the following manner: The milled button b is turned at top, till the twist index i o is at the mark o of the twist circle. Then the whole is turned in the collar H, till the ball a stand opposite to the mark o of the paper circle z o Q, and at the same time the ball t or d is touched. The observation is thus made. The ball t is first electrified, as just described, and thus a is repelled, and retiring twists the wire, settling, after a few oscillations, at such a distance as is proportional to the repulsion. The twist-index is now turned so as to force a nearer to t. The repulsion thus produced is estimated by adding the motion of the index to the angle at which the ball first stopped. Giving the index another, we have another repulsion, which is estimated in a similar way, and thus we obtain as many measures as required.
It is not necessary to make this instrument of very large dimensions; one 14 inches high, and five in diameter, of which the arm a g should occupy two inches and a half, will be sufficiently large for most purposes. The diameter of the glass cylinder must always be double the length of the arm a g, that the position of this may not be disturbed by the action of the glass.
Dr Robison considered this electrometer as one of the most valuable instruments that have been made, as it is not only extremely delicate, but gives absolute measures with the greatest accuracy. For all purposes in which only repulsions were to be measured, he preferred it to his own instrument described in Electricity, No. 206.
He, however, suggested several improvements in it, which are deserving of attention.
The bottom should be furnished with a round hole, admitting the lower end of the cylinder C c belonging to the lower pincer (when the wire is strained at both ends) to hang freely, by which means much tedious oscillation will be prevented. It is much more convenient to have the suspension wire strained at both ends; and it should extend as far below the arm as above it, and the lower extremity should be grasped by a pincer that turns by a milled head in a hole at the end of a slender spring. The instrument may then be speedily adjusted by placing the twist index at o, and gently turning the lower button till the ball a point exactly at o on the paper circle.
The instrument will be greatly improved, if, in place of the apparatus with the ball i, we substitute the piece represented at fig. 15, making some little changes in its construction. Thus, instead of the wire c d, is used the smallest glass tube that will admit of being varnished on the inside, which is done by drawing through it a silk thread dipped in varnish, made of lac.
The outside of the tube must also be varnished, and a brass ball d fixed at its lower end, and a slender wire, mounted by a ball, is to be inserted into the tube, so as to touch the ball below. The position of the ball d will not be liable to alteration, when the hole m is once stopped with the plug. In making delicate experiments, the upper ball c must be touched with the charger, represented at fig. 14, by which means the ball d is electrified. Then drawing out C by means of the forceps, the ball d is left completely inflated. In examining the electricity of the atmosphere, to which purpose this instrument is well adapted, the wire must be allowed to remain in the tube.
It was by means of this incomparable instrument, that M. Coulomb made the valuable experiments, to which we alluded in the article Electricity, when treating of the law of action of the electric fluid. By means of this electrometer, he also made his experiments on the dissipation of electricity into the air, and along imperfect conductors. He ascertained the law of dissipation into the air from bodies in contact, and the relation which this bore to the original repulsion, by first observing the gradual approach of the ball a towards i, in proportion as the electricity dissipated from both, and then slackening the twist index till the ball a resumed its original situation.
The following was the general result of Mr. Coulomb's experiments.
That the momentary dissipation of moderate degrees of electricity is proportional to the degree of electricity at the moment. He found that the dissipation is not sensibly affected by the state of the barometer or thermometer; nor is there any sensible difference of bodies of different sizes or different substances, or even different figures, provided that the electricity is very weak.
But he found that the dissipation was greatly affected by the different states of humidity of the air. In the scale of Saussure's hygrometer, the relation to the quantity of water which a cubic foot of air is capable of holding in solution is distinctly marked; the relation of this solution to the dissipation of electricity in Coulomb's experiments may hence be seen in the following table, the first column of which marks the degrees of Saussure's hygrometer, the second how many grains of water are dissolved in a cubic foot of air at each degree, and the third column shews the corresponding dissipation per minute.
| Degrees | Grains of Water | Dissipation | |---------|-----------------|-------------| | 69 | 6,197 | | | 75 | 7,295 | | | 80 | 8,045 | | | 87 | 9,221 | |
Hence it follows, that the dissipation is very nearly in the triplicate ratio of the moisture of the air. Thus if we make \( \frac{69}{75} = \frac{7,197}{6,180} \); \( m \) will be = 2,764. If we make \( \frac{69}{80} = \frac{7,197}{6,180} \); \( m \) will be = 2,764; and if we make \( \frac{69}{87} = \frac{7,197}{6,180} \); \( m \) will be = 3,61; or at a medium \( m \) will be = 3,40.
The immediate object, that M. Coulomb had in view in his experiments, was to ascertain the diminution of repulsion. He found that this, in a given state of the air, was a certain proportion of the whole repulsion taken at the moment of diminution, which is double the proportion of the density of the fluid; for the repulsions by which we judge of the dissipation are reciprocal, being exerted by every particle of fluid in the ball t of the electrometer, on every particle of fluid in the ball a. The diminution of repulsion is therefore proportional to the density of the electric fluid in each ball; and, as during the whole dissipation, the densities continue to have their original proportion, and as the diminution of repulsion is directly proportional to the diminution of the products of the densities, it is consequently directly proportional to the square of either. If we put \( d \) for the density, the mutual repulsion will be represented by \( d^2 \), and its momentary diminution by the fluxion of \( d^2 \), or \( 2d \times d = 2d^2 \). But \( 2d \times d : d^2 = 2d : d \). The diminution of repulsion observed by experiment will be to the whole repulsion, in double the proportion that the diminution of density, or the dissipation of fluid will have to the whole quantity of fluid at the moment of observation.
Let us, for instance, suppose the observed diminution of repulsion to be \( \frac{1}{8} \); we may conclude, that the quantity of fluid lost by dissipation is \( \frac{1}{8} \). M. Coulomb did not examine the proportion of the dissipations from bodies of various sizes. But we know, that if two spheres communicate by a very long canal, their superficial densities, and the tendencies of fluid to escape from them, are inversely as the diameters of the spheres. Now, in a body that has twice the diameter of another body, the surface of the former is quadruple of that of the latter; and though the tendency of fluid to escape from the former is only the half of its tendency to escape from the latter, yet the greater surface of the former may so far make up for its smaller density, that the diffusion of fluid from a large sphere may in fact be greater than that from a small one in the same given time.
We have remarked above, that these experiments were made in a particular state of the air; and the law of diffusion ascertained by them is of course adapted only to that given state. In a different state of the air, even if this should be impregnated with the same proportion of moisture, the law of diffusion may be different. The inference which M. Coulomb expected to draw from his experiments was, that the ratio of diffusion would prove to be less than the cube of the quantity of water held in solution, except when that quantity of water was what the air was capable of holding in solution at the given temperature.
This is agreeable to observation; for we know that air which is considered as dry, that is, when it is not nearly saturated with moisture, is the most favourable to electrical phenomena.
Such is the general result of Coulomb's experiments on the diffusion of electricity into the air.
The method in which M. Coulomb examined the diffusion along imperfect conductors, by means of this instrument, was, by completely inflating the ball, and then after observing the loss sustained by a body in contact with it from the air, sliding a metallic rod down the inflating stalk, till the diffusion began to exceed what took place only by the air.
From his experiments respecting the diffusion along imperfect conductors, he found that this took place in a different manner from that in which electricity escaped by communication with the contiguous air. The electricity seems to be diffused chiefly along the surface of the conductor, and appears principally to be produced by the moisture that is more or less attached to it. M. Coulomb illustrates this in the following manner.
Water is found to adhere to the surface of all bodies from which it is prevented by adhesion from escaping when the bodies are electrified, and is thus rendered capable of receiving a greater degree of electric power. Let us suppose that the particles of moisture are disposed uniformly over the surface, with intervals between them; the electricity that is communicated to one particle, must acquire a certain degree of density, before it can fly from this particle to the next, across the intervening inflating space. When an imperfect conductor of this kind is electrified at one extremity, the communicated electricity, in passing to the other extremity, must be weakened every step in passing from particle to particle.
Suppose we have three adjacent particles, which we may call \(a\), \(b\), and \(c\); we infer from No. 374, of the article Electricity, that the motion of \(b\) is sensibly effected, only by the difference of \(a\) and \(c\); and therefore the passage of electric fluid from \(b\) to \(c\), requires that this difference be superior, or at least equal to the force necessary for clearing this coercive interval. Let a particle pass over. The density of fluid of the particle \(b\) is diminished, while the density of the particle on the other side of \(a\) remains as before. Therefore some fluid will pass from \(a\) to \(b\), and from the particle preceding \(a\) to \(a\); and so on, till we come to the electrified end of this conductor. It is plain, from this consideration, that we must at last arrive at a particle beyond \(c\), where the whole repulsion of the preceding
particles is just sufficient to clear the coercive interval. Some fluid will come over; and the repulsion of this, acting now in the opposite direction, will prevent any fluid from coming to supply its place in the particle which it has just quitted; the transference of fluid will therefore stop here, and beyond this point the inflation will be complete. Hence we perceive that there is a mathematical relation between the inflating power, and the length of the canal; and this may be ascertained by the theory which we adopted in the article Electricity. We shall here give an instance of this investigation; and, for the sake of simplicity, we shall take a very probable case, viz. where the inflating interval, or, as we may more properly call it, the coercive interval, is equal in every part of the canal.
Let \(R\) represent the coercive power of the inflator, or the degree of force required to clear the coercive interval between two particles. Suppose a ball \(C\), fig. 16, suspended by a silk thread \(AB\); and let us denote the quantity of redundant fluid in the ball by \(C\), and let the densities at the different points of the canal be denoted by \(AD\), \(PD\), &c., ordinates to some curve \(DdB\), cutting the axis in \(B\), the point where the thread \(AB\) begins to inflate completely. Let \(PP\) be an element of the axis; draw the ordinate \(PF\), a tangent to the curve \(dfF\), the normal \(DE\), and draw \(Fe\) perpendicular to \(PD\). Suppose \(AC=x\), \(AP=x\), and \(PD=y\).
Then we shall have \(PP=x\), and \(dE=y\). It was shewn in No. 374, of the article Electricity, that the only sensible action of the fluid on a particle at \(P\) is \(-\frac{yy}{x}\), when the action of the redundant fluid in the globe on the particle at \(P\), having the density \(y\), is denoted by \(\frac{Cy}{(r+x)^2}\). Therefore \(\frac{yy}{x}\) is \(=R\), the coercive power of the thread, which is supposed to be constant, \(\frac{PD \times dE}{PP}\) is therefore equal to some constant line \(R\). But \(PP\) (or \(Fe\)) : \(dE = PD : PE\). The subnormal \(PE\), is therefore a constant line. But as this is the property of a parabola, the curve of density \(DdB\) must be a parabola, of which \(2PE = 2R\), is the parameter.
Cor. 1.—The densities at different points of an imperfect conductor are in the subduplicate ratio of their distances from the point of complete inflation: for \(PD^2 : AD^2 = BP : BA\).
Cor. 2.—The lengths of canal requisite for inflating different densities of the electric fluid are in the duplicate ratio of their densities; for \(AB = \frac{AD^2}{2PE}\), and \(PE\) is a constant quantity.
Cor. 3.—The length of canal requisite for inflation is inversely as its coercive power, and may be represented by \(\frac{D^2}{R}\). For \(AB = \frac{DA^2}{2PE} = \frac{D^2}{2R}\).
If we reflect on this theory, we shall perceive, that our formulæ determine the distribution of fluid along the surface of an imperfect conductor, only in a certain manner, supposing that the ball \(C\) has received a certain determinate portion of fluid, for this portion diffusing itself, particle by particle, through the conducting matter, will extend to \(b\) in such a manner, as that the repulsion shall be everywhere in equilibrium with the coercive power of the inflating interval, taken at a maximum. We must here remark that this repulsion is not active, but only coercive, and may be compared to the repulsion afforded by viscosity or friction. Any repulsion of electric fluid, which falls short of this, will not disturb the stability of the fluid that is spread along the canal, according to any law whatever. So that if $AD$ represent the electric density of the globe, and remain constant, any curve of density will answer,
$$\frac{d^2}{x^2} \text{be everywhere less than } R.$$ It is therefore an indeterminate problem, to assign in general the disposition of fluid in the canal. The density is as the ordinates of a parabola on this supposition only, that the maximum of $R$ is everywhere the same. And, in this case, the distance $AB$ is a minimum; for, in other cases of density we must have
$$\frac{d^2}{x^2} \text{less than } R.$$ If, therefore, we vary a single element of the curve $DdB$, in order that the stability of the fluid may not be disturbed, having $d$ constant, we must necessarily have $x$ larger, that $\frac{d^2}{x^2}$ may still be less than $R$; that is, we must lengthen the axis.
The reasonings which have thus been deduced from theory, were confirmed by M. Coulomb in a numerous set of experiments. These are chiefly valuable for having stated the relation that subsists between the electric density, and the length of support necessary for complete inflation. But as M. Coulomb has not given us the scale of his electrometer, according to which the absolute measures of the densities were determined, the experiments can be of but little use till this be known.
We hinted, at the end of the theoretical part of Electricity, that the theory of Volta's condenser might be more satisfactorily explained after we had considered the above experiments of Coulomb. The account which we gave of the condenser in Chap. xiii. of that article, (chiefly from Cavallo), was the only one we could properly give in that early part of our view of the science. We are now prepared for a more scientific account of the effects of that instrument. The following is nearly the manner in which Dr Robison considered the subject.
Let the cover of an electrophorus be furnished with a graduated electrometer, such as may indicate the proportional degrees of electricity; electrify it positively to any degree, we shall suppose fix, while it is held in the hand, at a little distance, directly over a metallic plate lying on a wine glass, or such like inflating fluid, but made to communicate with the ground by a wire. Now bring it gradually down towards the plate. Theory teaches, and we see it confirmed by experiment, that the electrometer will gradually subside, and will perhaps fall to $2^\circ$, before the electricity is communicated in a spark; but let us stop it before this happens; the attraction of the lying plate produces a compensation of four degrees of the mutual repulsion of the parts of the cover, by condensing the fluid on its inferior surface, and forming a deficient stratum above. This needs no farther explanation, after what we said under Electricity, on the charging of coated glass plates. Now we may suppose that the escape of the fluid from this body into the air begins as soon as it is electrified to $6^\circ$, and that it will fly to the inflated plate with the degree $2$, if it be brought nearer. But if we can prevent this communication to the inflated plate, by interposing an electric, we may electrify the cover again, while so near the metallic plate, to $6^\circ$, before it will pass off into the air. If now it be removed from the lying plate, the fluid would cause the electrometer to rise to $10^\circ$, if it did not immediately pass off; and an electric excitement of any kind which could raise this body only to $6^\circ$ by its intensity, will, by means of this apparatus, raise it to the degree $10$, if it be sufficiently copious in extent. If we do the same thing when the wire which connects the lying plate with the ground is taken away, we know that the same diminution of the electricity of the other plate cannot be produced by bringing it down near the lying inflated plate.
The theory of Volta's condenser now becomes very simple. M. Volta seems to have obscured his conceptions of it, by being intent on the electrophorus which he had lately invented, and was thus led into fruitless attempts to explain the advantages of the imperfect conductor above the perfect insulator. But the condensing apparatus is wholly different from an electrophorus; its operations are more analogous to those of a coated plate not charged, and insulated only on one side; and such a coated plate lying on a table will be a complete condenser, if the upper coating be of the same dimensions as the plate of the condenser. All the directions given by M. Volta for preparing the imperfect conductors prove, that the effect produced is to make them as perfect conductors as possible for any degree of electricity that exceeds a certain small intensity, but such as shall not suffer this very weak electricity to clear the first step of the conducting space. The marble must be thoroughly dried, and even heated in an oven, and either used in this warm state, or must be varnished, so as to prevent the reabsorption of moisture. We know that marble of slender dimensions, so as to be completely dried throughout, will not conduct electricity till it has again become moist. A thick piece of marble is rendered dry only superficially, and still conducts internally. It is then in the best possible state for a condenser. The same is the case with dry unbaked wood. Varnishing the upper surface of a piece of marble or wood is equivalent to covering it with a thin glass plate. Now by this method of covering the top of the marble, a book, or even the table, with a piece of clean dry silk, they all become most perfect condensers. This view of the matter has great advantage. We learn from it how to form a condensing apparatus much more simple and at the same time much more efficacious. We require only the simple moveable plate, which must be covered on the underside with a very thin coating of the finest coach-painters varnish. By connecting this, by a wire, with the substance whose weak electricity is to be examined, this electricity will be raised in the proportion of the thickness of the varnish to the fourth of the plate's diameter. This condensation will be produced by detaching the wire from the insulating handle of the condensing plate, and then lifting this from the table on which it was lying. It will then afford sparks, though the original electricity Electro-electricity was not strong enough to affect the most delicate electrometer.
**ELECTROPHORUS.** See Electricity Index.
**ELECTRUM,** in Natural History. See Amber.
**ELICTUARY,** in Pharmacy, a form of medicine composed of powders and other ingredients, incorporated with some conserve, honey, or syrup; to be divided into doses, like lozenges, when taken.
Vindius observes, that all the remedies prescribed for the sick, as well as the confections taken by way of regale, were called by the Greeks *eleoquartz,* and *eleoquartz,* of the verb *aixos,* "I like;" whence, says he, was formed the Latin *eleoquarium,* and afterwards *electuarium.* This conjecture he supports from the laws of Sicily, where it is ordained, that *eleoquaries,* syrups, and other remedies, be prepared after the legal manner. The Bollandists, who relate this etymology, seem to confirm it. For the composition and different sorts of electuaries, see Pharmacy.
**ELEEMOSYNA Caricarum,** or pro Aratri, or Aratri, in our ancient customs, a penny which King Ethelred ordered to be paid for every plough in England towards the support of the poor. Sometimes it is also called *eleemofynia regis,* because first appointed by the king.
**ELEEMOSYNARIUS,** in our old writers, is used for the almoner or peculiar officer who received the eleemofynary rents and gifts, and distributed them to pious and charitable uses. There was such an officer in all religious houses. The bishops also used to have their almoners, as now the king has.
**ELEGANCE,** (from *eligo,* "I choose,") denotes a manner of doing or saying things politely, agreeably, and with choice. With choice, so as to rise above the common manners; politely, so as to strike people of delicate taste; and agreeably, so as to diffuse a relish which gratifies every body.
**ELEGANCE,** in oratory and composition, an ornament of politeness and agreeableness shown in any discourse, with such a choice of rich and happy expressions, as to rise politely above the common manners, so as to strike people of a delicate taste.
It is observed, that elegance, though irregular, is preferable to regularity without elegance: that is, by being so scrupulous of grammatical construction, we lose certain licences wherein the elegance of language consists.
**ELEGIA,** in ancient poetry, anything belonging to elegy. See Elegy.
**ELEGIT,** in Law, a writ of execution, which lies for a person who has recovered debt or damages; or upon a recognizance in any court against a defendant that is not able to satisfy the same in his goods.
**ELEGY,** a mournful and plaintive kind of poem. See the article Poetry.
**ELEMENTS,** in Physics, the first principles of which all bodies in the system of nature are composed.
These are supposed to be few in number, unchangeable, and by their combinations to produce that extensive variety of objects to be met with in the works of nature.
That there is in reality some foundation for this doctrine of elementary bodies is plain; for there are some principles evidently exempted from every change or decay, and which can be mixed or changed into different elements, forms or matter. A person who surveys the works of nature in an attentive manner, may perhaps form a contrary opinion, when he considers the numerous tribes of animals, plants, and animals, with the wonderful variety that appears among them in almost every instance. He may from thence be induced to conclude, that nature employs a vast variety of materials in producing such prodigious diversity. But let him inquire into the origin of this apparent diversity, and he will find that these bodies which seem the most different from each other are composed nearly of the same elements. Thus the blood, chyle, milk, urine, &c., as well as the various solid parts of animals, are all composed of one particular substance; grass, for instance, by the affluence of air and water, and even sometimes of very infipid kinds of grass. The same simplicity prevails itself in the original composition of the nourishment of vegetables, notwithstanding the variety among them with respect to hardness, softness, elasticity, taste, odour, and medical qualities. They chiefly depend, for these, upon water and the light of the sun; and the same simplicity must take place in animals that are fed on vegetables. The analysis of animal substances confirms this hypothesis; for they can all be reduced into a few principles, which are the same in all, and only differ with regard to the proportions in which they are combined. With regard to animals, the case appears to be the same; and the more we are acquainted with them, the more reason we have to believe that the variety in their origin is very small.
Notwithstanding the infinite variety of natural productions, therefore, it appears, that the materials employed in their formation are but few; that these are uniformly and certainly the same, totally exempted from any change or decay; and that the constant and gradual change of one body into another is produced by the various separations and combinations of the original and elementary parts, which is plain from the regularity and uniformity of nature at all times. There is a change of forms and combinations through which it passes, and this has been the case from the earliest accounts of time; the productions of nature have always been of the same kind, and succeeded one another in the same order. If we examine an oak, for instance, we find it composed of the same matter with that of any other that has existed from the earliest ages. This regularity and uniformity in the course of nature shows that the elementary parts of bodies are permanent and unchangeable; for if these elementary particles which constituted an oak some thousand years ago, had been undergoing any gradual decay, the oaks of the present times would have been found considerably different from those that existed long ago; but as no difference has been observed, it would seem that the ultimate elements of bodies have always continued the same.
Reflections of this kind have suggested an idea of several principal elements of which all other bodies are composed, which by their various combinations furnished all the variety of natural bodies. Democritus, and other great philosophers of antiquity, fixed the number to four, which have retained the name of elements ever since. These are, fire, air, earth, and water; each of which they imagined was naturally disposed. Elements disposed to hold its own place in the universe. Thus, the earth, as heaviest, naturally tended towards the centre, and occupied the lower parts; the water, as approaching next to it in gravity, was spread chiefly on the outside of the earth: the air, being more subtle and rare, occupied the middle place; while the fire, being still more subtle and active, receded to the greatest distance of all, and was supposed to compose the planets and stars. This system was extended to all the productions of nature. Meteors were produced from a combination of fire and air; animals were considered as composed of earth and water; and those that were warm had likewise a proportion of the element of fire. Thus they went on, explaining some of the most striking qualities of the several productions of nature from the different proportions of the four elements they contained.
But though this system appears not at all defective of beauty and propriety, and on this account has been long received, we know from modern discoveries that these four substances are not really elementary bodies; nor do they answer our purpose in forming a system, as we know too little of the intimate structure and texture of them to enable us to explain other bodies by them.
Any other attempts that have been made to assign the number of elementary bodies have been much less fortunate. The older chemists, with Paracelsus at their head, pretend to speak of four elementary bodies, salt, sulphur, earth, and mercury: but when we attempt to form an idea of what they mean, we find it very perplexed; and that the expressions concerning them are enveloped in so much obscurity, that they cannot be comprehended; and the theory is built entirely upon experiments made on metallic substances.
Attempts have been made by some to show that the elements, whatever they are, must necessarily be invisible or imperceptible by any of our senses. An inquiry into their number or properties therefore must be attended with very little success; and all the knowledge we can have upon the subject must be drawn from a view of their combinations, and reasoning analogically from the transmutations we observe to take place in nature. The modern discoveries in aerology have enabled us to proceed farther in this way than what it was possible for the ancient philosophers to do. We now find that all the different kinds of air are composed of that invisible and subtle fluid named heat, united in a certain way with some other substance: by which union the compound acquires the properties of gravitation, expansion, rarefaction, &c. for pure heat, unless when united with some terrestrial substance, neither gravitates nor expands. This is evident from the phenomena of the burning glass, where the light concentrated in the focus will neither heat the air nor water, unless it meets with something with which it can form a permanent union. Heat therefore is justly to be considered as one of the original elements; being always capable of uniting with bodies, and of being extricated from them unchanged; while the same bodies are by their union with it changed into various forms; water, for instance, into ice or vapour, both of which return into their original state by the abstraction or addition of heat in a certain degree. Hence it becomes almost natural to conclude, that there are only two elements in the universe: and this opinion we find adopted by several philosophers, particularly the count de Treslan in his Essay on the Electric Fluid. According to his doctrine, two primitive material substances seem to exist in nature; one that incessantly acts, and to which it is essential to be in motion; the other absolutely passive, and whose nature it is to be inert, and move entirely as directed by the former. Should this doctrine be adopted, little difficulty would occur in determining the active matter to be that universal fluid, which, in its various modifications of light, heat, and electricity, has such a share in the operations of nature. But in fixing on the passive element we are greatly embarrassed; nor are the discoveries in aerology or any other science as yet able to remove the difficulty entirely. According to the doctrines which long prevailed among chemical philosophers, there are three things that seem to be unchangeable, viz., earth; phlogiston; and that invisible, though terrestrial and gravitating principle, called by the antiphlogitians the oxygénous or acidifying principle, and by the phlogitians the basis of dephlogisticated air. In our experiments, say they, on the first, we find that earth, though vitrified by the most intense fire, may be recovered in its proper form: and some very pure earths, particularly magnesia alba, cannot be changed even in the focus of the most powerful mirror. In like manner we may distillate charcoal in vacuo by the solar rays, and the compound is inflammable air: we may decompose this compound by a metallic calx, and we have our charcoal again unchanged, for all metals contain charcoal in substance. Let us try to destroy it by common fire, and we have it then in the fixed air produced, from which it may be recovered unchanged by means of the electric spark. With the basis of dephlogisticated air the case is still more difficult; for we cannot by any means procure a flight of it by itself. We may combine it with heat, and we have dephlogisticated air; to the compound we may add charcoal, and we have fixed air: by decomposing the former by burning iron in it, we have the metal greatly increased in weight by some unknown substance: and if we attempt to separate the latter, we have water, or some kind of vapour which still conceals it from our view.
In some experiments which were made by the ingenious Mr Watt, it was found that nitrous acid might be dephlogisticated by the purest earth or metallic calx; whence, according to this doctrine, it is not unreasonable to suppose that phlogiston may be only a certain modification of earth, and not an element distinct from it: but with regard to the basis of dephlogisticated air, no experiment has ever shown that it can either be procured by itself, or changed into any other substance; so that it appears to have the nature of an element as much as light or heat. Though we should therefore be inclined to divide the whole matter of the universe into two classes, the one active and the other acted upon, we must allow that the passive matter even on this earth is not precisely of the same kind: much less are we to extend our speculations in this respect to the celestial regions; for who can determine whether the substance of the moon is the same with that of our earth, or that the elements of Jupiter are the same with those of Saturn? There is even a difficulty with regard to the division which seems so well established, viz., of matter in general into active and passive; for no person can prove, that the matter which is active in one case may not be passive in another, and occasionally resume its activity. Something like this certainly happens in the case of the electric fluid, which is modified into heat or light, according to different circumstances; and we cannot know but it is the very same substance that constitutes the most solid bodies. This opinion at least did not seem absurd to Sir Isaac Newton, who propounded it as a query, Whether gross bodies and light were not convertible into one another? The end of our inquiries on this subject therefore must be, That the universe may be composed of many elements, or of one element; and of the nature of these elements, or of the single one, we know nothing.