RAMSAY

RAMSAY, The Rev. James, so justly celebrated for his philanthropy, was born on the 25th of July 1733, at Frasersburgh, a small town in the county of Aberdeen, North Britain. His descent was honourable, being, through his father, from the Ramsays of Melrose in Banffshire, and through his mother, from the Ogilvies of Purie in Angus. His parents were of characters the most respectable, but in circumstances by no means affluent. From his earliest years he discovered a serious disposition, and a strong thirst for knowledge; and after passing through the course of a Scotch grammar school education, he was inclined to pursue the studies requisite to fit him for the profession of a clergyman; an inclination with which the wishes of his mother, a woman of eminent piety, powerfully concurred. Several circumstances, however, conspired to divert him for a time from his favourite pursuit.

He was educated in the episcopal persuasion; and having been unhappy enough to lose his father while yet very young, he found, upon his advancing towards the state of manhood, that the joint fortunes of himself and his mother could not bear the expence of a regular education in either of the universities of Oxford or Cambridge, which he doubtless thought absolutely necessary to one who aspired to respectability in the church of England. Yielding therefore to necessity, he resolved to study surgery and pharmacy; and was with this view bound apprentice to Dr Findlay, a physician (A) in Frasersburgh. But though obliged to relinquish for a time his favourite studies, he did not think ignorance excusable in a surgeon more than in a clergyman, or conceive that he could ever become eminent in the profession in which circumstances had placed him, merely by skill in setting a bone or compounding a medicine. He determined therefore, with the full approbation of his master, who

Ray. who very soon discovered his talents for literature, to make himself acquainted with at least the outlines of the liberal arts and sciences; and with this view he repaired in 1750 to the King's College and university of Aberdeen, where he obtained one of the bursaries or exhibitions which are there annually bestowed upon such candidates for them as display the most accurate knowledge of the Latin language. The small sum of five pounds, however (which none of these bursaries exceed), was still inadequate to the expence of residence in college; but our young student was soon to obtain a more valuable exhibition, and to obtain it likewise by his own merit.

During the long vacation he returned to his master Dr Findlay, and was by him intrusted with a very desperate case in surgery, of which his management may be said to have laid the foundation of his future fortunes. A female servant of one of the judges of the Court of Session, who, when the court was not sitting, resided in the neighbourhood of Erasersburgh, had been so dreadfully gored by a bull, that hardly any hopes were entertained of her recovery; but Mr Ramsay, to whose care she was entirely left, treated the wound with such skilful attention, that, contrary to general expectation, his patient recovered. This attracted the judge's notice, who having informed himself of the young man's circumstances and character, recommended him so effectually to Sir Alexander Ramsay of Balmain, that he presented him with a bursary of 15 pounds a-year, which commenced at the next session or term, in the same college.

He now prosecuted his studies with comfort: and though he was detained in college a year longer than is usual, being obliged, upon his acceptance of a second bursary, to begin his course anew, he always considered this as a fortunate circumstance, because it gave him the celebrated Dr Reid three years for his preceptor. To that great and amiable philosopher he so recommended himself by his talents, his industry, and his virtues, that he was honoured with his friendship to the day of his death. Nor was it only to his masters that his conduct recommended him; Sir Alexander Ramsay, whom he visited during some of the vacations, was so well pleased with his conversation, that he promised him another bursary, in his gift, of 251. a-year, to commence immediately on the expiration of that which he enjoyed. This promise he performed in the beginning of the year 1755; and at the solicitation of Dr Findlay, even paid the money per advance to enable the exhibitioner to travel for the purpose of improving himself in his profession.

Thus provided, Mr Ramsay went to London, and studied surgery and pharmacy under the auspices of Dr Macaulay; in whose family he lived for two years, caressed and esteemed both by him and by his lady. Afterwards, having passed the usual examination at Surgeons-hall, he served in his medical capacity for several years in the royal navy; but how long he was continued in the station of a mate, or when and by whom he was first appointed surgeon, we have not been able to learn. We can say, however, upon the best authority, that by his humane and diligent discharge of his duty in either station, he endeared himself to the seamen, and acquired the esteem of his officers.

Of his humanity there is indeed one memorable instance.

stance, which must not be omitted. Whilst he acted as surgeon of the Arundel, then commanded by Captain (now Vice-admiral Sir Charles) Middleton, a slave-ship on her passage from Africa to the West Indies fell in with the fleet to which the Arundel belonged. An epidemical distemper, too common in such vessels, had swept away not only a great number of the unfortunate negroes, but also many of the ship's crew, and among others the surgeon. In this distressed situation the commander of the Guinea ship applied to the English commodore for medical assistance; but not a surgeon or surgeon's mate in the whole fleet, except Mr Ramsay, would expose himself to the contagion of so dangerous a distemper. Prompted, however, by his own innate benevolence, and fully authorised by his no less benevolent commander, the surgeon of the Arundel, regardless of personal danger, and trusting in that God to whom mercy is more acceptable than sacrifice, went on board the infected ship, visited all the patients, and remained long enough to leave behind him written directions for their future treatment. If a cup of cold water given in charity be entitled to a reward, how much more such an action as this? But the rewards of Christianity are not immediate. Mr Ramsay indeed escaped the contagion; but on his return to his own ship, just as he had got on the deck, he fell and broke his thigh-bone; by which he was confined to his apartment for ten months, and rendered in a small degree lame through the remainder of his life.

The fearless humanity which he displayed on this occasion gained him the friendship and esteem of Sir Charles Middleton, which no future action of his life had the smallest tendency to impair; but the fracture of his thigh-bone and his subsequent lameness determined him to quit the navy, and once more turn his thoughts towards the church. Accordingly, while the Arundel lay at St Christopher's, he opened his views to some of the principal inhabitants of that island, by whom he was so strongly recommended to the bishop of London, that on his coming home with Sir Charles Middleton, who warmly joined in the recommendation, he was admitted into orders; after which he immediately returned to St Christopher's, where he was presented by the governor to two rectories, valued at 7001. a-year.

As soon as he took possession of his livings, in 1763, he married Miss Rebecca Akers, the daughter of a planter of the best family-connections in the island, and began to regulate his household on the pious plan inculcated in his Essay on the Treatment and Conversion of the African Slaves in the British Sugar Colonies. He summoned all his own slaves daily to the prayers of the family, when he took an opportunity of pointing out to them their duty in the plainest terms, reproofing those that had done amiss, and commending such as had shown any thing like virtue; but he confessed that his occasions for reproof were more frequent than for commendation. As became his office and character, he inculcated upon others what he practised himself, and knew to be equally the duty of all. "On his first settlement as a minister in the West Indies, he made some public attempts to instruct slaves. He began to draw up some easy plain discourses for their instruction. He invited them to attend, on Sunday, at particular hours. He appointed hours at home to instruct such sensible slaves

Ramsay. as would of themselves attend. He repeatedly exhorted their masters to encourage such in their attendance. He recommended the French custom, of beginning and ending work by prayer. But inconceivable is the listlessness with which he was heard, and bitter was the censure heaped on him in return. It was quickly suggested, and generally believed, that he wanted to interrupt the work of slaves, to give them time, forsooth, to say their prayers; that he aimed at the making of them Christians, to render them incapable of being good slaves. In one word, he stood, in opinion, a rebel convict against the interest and majesty of plantership. And as the Jews say, that in every punishment, with which they have been proved, since the bondage of Egypt, there has been an ounce of the golden calf of Horeb; so might he say, that in every instance of prejudice (and they were not a few) with which, till within a year or two of his departure from the country, he was exercised, there was an ounce of his fruitless attempts to improve the minds of slaves. In the bidding prayer, he had inserted a petition for the conversion of those persons. But it was deemed so disagreeable a memento, that several white people, on account of it, left off attending divine service. He was obliged to omit the prayer entirely, to try and bring them back. In short, neither were the slaves at that time desirous of being taught, nor were their masters inclined to encourage them."

That he was hurt by this neglect cannot be questioned, for he had a mind benevolent, warm, and irritable; but he still retained many friends amongst the most worthy members of the community; and as he was conscious of having done nothing more than his duty, he consoled himself with reflecting, that those are "blessed whom men revile, and persecute, and speak all manner of evil against falsely, for the sake of the gospel."

Although his serious studies were now theological, he considered himself as answerable to God, his country, and his own family, for a proper use of every branch of knowledge which he possessed. He therefore took the charge of several plantations around him in the capacity of a medical practitioner; and attended them with unremitting diligence, and with great success. Thus he lived till the year 1777, when relinquishing the practice of physic entirely, he paid a visit to the place of his nativity, which he had not seen since 1755. His mother, whose latter days he had made comfortable by a handsome annuity, had been dead for some years; but he rewarded all who had been attentive to her, or in early life serviceable to himself; and he continued the pension to a sister who had a numerous family, for which her husband was unable to provide.

After remaining three weeks in Scotland, and near a year in England, during which time he was admitted into the confidence of Lord George Germaine, secretary of state for the American department, Mr Ramsay was appointed chaplain to Admiral Barrington, then going out to take a command in the West Indies. Under this gallant officer, and afterwards under Lord Rodney, he was present at several engagements, where he displayed a fortitude and zeal for the honour of his country which would not have disgraced the oldest admiral. To the navy, indeed, he seems to have been strongly attached; and he wrote, at an early period of his life, an Essay on the Duty and Qualifications of a Sea-officer, with such a knowledge of the service as

would have done honour to the pen of the most experienced commander. Of the first edition of this essay the profits were by its benevolent author appropriated to the Magdalen and British lying-in hospitals, as those of the second and third (which last was published about the period of which we now write) were to the maritime school, or, in the event of its failure, to the maritime society.

Although caressed by both the admirals under whom he served, and having such influence with the latter as to be able to render essential services to the Jews and other persons whom he thought harshly treated at the capture of St Eustatius, Mr Ramsay once more quitted the sea-service, and retired to his pastoral charge in the island of St Christopher's. There, however, though the former animosities against him had entirely subsided, and though his friendship was now solicited by every person of consequence in the island, he remained but a little while. Sick of the life of a planter and of the prospect of slavery around him, he resigned his livings, bade adieu to the island, and returned to England with his wife and family in the end of the year 1781. Immediately on his arrival, he was, through the interest of his steady friend Sir Charles Middleton, presented to the livings of Teston and Nettleshead in the county of Kent.

Here he was soon determined, by the advice of those whom he most respected, to publish an Essay, which had been written many years before, on the Treatment and Conversion of African Slaves in the British Sugar Colonies. The controversy in which this publication involved him, and the acrimony with which it was carried on, are so fresh in the memory of all our readers, that no man who thinks of the narrow limits within which our biographical articles must be confined, will blame us for not entering into a detail of the particulars.—Torrents of obloquy were poured upon the benevolent author by writers who were unfair enough to conceal their names; and it must be confessed, that his replies abounded with sarcasms, which the most rational friends to the cause which he supported would not have been sorry to see blotted from his pages. The provocation, however, which he received was great; and Mr Ramsay, though an amiable, virtuous, and pious man, had a warmth of temper, which, though not deserving of praise, will be censured by none who reflect on the frailties of our common nature. That the particular calumnies propagated against him on this occasion were wholly groundless, it is impossible to doubt, if we admit him to have been possessed of common understanding. When some years ago a story was circulated, of Swift's having, when prebendary of Kilroot, been convicted before a magistrate of an attempt to commit a rape on the body of one of his parishioners, it was thought a sufficient confutation of the calumny to put the retailer of it in mind, that the dean of St Patrick's, though detested by the most powerful faction in the kingdom, lampooned without dread, and with great severity, the dean of Ferns for the very crime, of which, had this anecdote been true, he must have been conscious that all Ireland knew himself to be guilty! Such conduct cannot be reconciled to common sense. Had Swift been a ravisher, though he might have been penitent, and reasoned in general terms against giving way to such licentious passions, he would never have satirised

Ramsay, a particular person for the crime of which he himself stood convicted. In like manner, had Mr Ramsay been a tyrant to his own slaves, though he might have argued against slavery in the abstract, on the broad basis of virtue and religion, he never could have arraigned for similar cruelty a number of individuals in the very island which witnessed his own enormities.

But the melancholy part of the narrative is behind. The agitation given to his mind by these calumnies, and the fatigues he underwent in his endeavours to rescue from misery the most helpless portion of the human race, contributed to shorten a life in no common degree useful. He had been for some time afflicted with a pain in his stomach, for which he was prevailed upon, though with great reluctance, to try the effects of air and exercise, by attempting a journey of 100 miles. But in London, being seized with a violent vomiting of blood, he was unable either to proceed or to be removed home; and in the house of Sir Charles Middleton he ended his days, on the 20th of July 1789, amidst the groans of his family, and the tears of many friends.—Thus died a man, of whom it is not too much to say, that "the blessing of many that were ready to perish came upon him;" for whatever be the fate of the slave-trade (see SLAVERY), it is certain that his writings have contributed much to meliorate the treatment of slaves. He left behind him a widow and three daughters: and his works, besides those to which we have alluded, consist of a volume of Sea-sermons, preached on board his majesty's ship the Prince of Wales, which show him to have been a master of true pulpit eloquence; and a Treatise on Signals, which was certainly written, and we think printed, though we know not whether it was ever published.

RAMSDEN'S MACHINE for Dividing MATHEMATICAL INSTRUMENTS, is an invention by which these divisions can be performed with exceeding great accuracy, such as would formerly have been deemed incredible. On discovering the method of constructing this machine, its inventor, Mr Ramsden of Piccadilly, received 615l. from the commissioners of longitude; engaging himself to instruct a certain number of persons, not exceeding ten, in the method of making and using this machine from the 28th October 1775 to 28th October 1777: also binding himself to divide all octants and sextants by the same engine, at the rate of three shillings for each octant, and six shillings for each brass sextant, with Nonius's divisions to half minutes, for as long time as the commissioners should think proper to let the engine remain in his possession. Of this sum of 615l. paid to Mr Ramsden, 300l. was given him as a reward for the improvement made by him in discovering the engine, and the remaining 315l. for his giving up the property of it to the commissioners. The following description of the engine, is that given upon oath by Mr Ramsden himself.

"This engine consists of a large wheel of bell-metal, supported on a mahogany stand, having three legs which are strongly connected together by braces, so as to make it perfectly steady. On each leg of the stand is placed a conical friction pulley, whereon the dividing wheel rests: to prevent the wheel from sliding off the friction-pulleys, the bell-metal centre under it turns in a socket on the top of the stand.

"The circumference of the wheel is ratched or cut (by a method which will be described hereafter) into

2160 teeth, in which an endless screw acts. Six revolutions of the screw will move the wheel a space equal to one degree.

Now a circle of brass being fixed on the screw arbor, having its circumference divided into 60 parts, each division will consequently answer to a motion of the wheel of 10 seconds, six of them will be equal to a minute, &c.

"Several different arbors of tempered steel are truly ground into the socket in the centre of the wheel. The upper parts of the arbors that stand above the plane are turned of various sizes, to suit the centres of different pieces of work to be divided.

"When any instrument is to be divided, the centre of it is very exactly fitted on one of these arbors; and the instrument is fixed down to the plane of the dividing wheel, by means of screws, which fit into holes made in the radii of the wheel for that purpose.

"The instrument being thus fitted on the plane of the wheel, the frame which carries the dividing-point is connected at one end by finger-screws with the frame which carries the endless screw; while the other end embraces that part of the steel arbor, which stands above the instrument to be divided, by an angular notch in a piece of hardened steel; by this means both ends of the frame are kept perfectly steady and free from any shake.

"The frame carrying the dividing-point, or tracer, is made to slide on the frame which carries the endless screw to any distance from the centre of the wheel, as the radius of the instrument to be divided may require, and may be there fastened by tightening two clamps; and the dividing-point or tracer being connected with the clamps by the double-jointed frame, admits a free and easy motion towards or from the centre for cutting the divisions, without any lateral shake.

"From what has been said, it appears, that an instrument thus fitted on the dividing-wheel may be moved to any angle by the screw and divided circle on its arbor, and that this angle may be marked on the limb of the instrument with the greatest exactness by the dividing-point or tracer, which can only move in a direct line tending to the centre, and is altogether freed from those inconveniences that attend cutting by means of a straight edge. This method of drawing lines will also prevent any error that might arise from an expansion or contraction of the metal during the time of dividing.

"The screw-frame is fixed on the top of a conical pillar, which turns freely round its axis, and also moves freely towards or from the centre of the wheel, so that the screw-frame may be entirely guided by the frame which connects it with the centre: by this means any excentricity of the wheel and arbor would not produce any error in the dividing; and, by a particular contrivance (which will be described hereafter), the screw when pressed against the teeth of the wheel always moves parallel to itself; so that a line joining the centre of the arbor and the tracer continued, will always make equal angles with the screw.

"Figure 1. represents a perspective view of the engine.

"Fig. 2. is a plan, of which fig. 3. represents a section on the line NA.

"The large wheel A is 45 inches in diameter, and has

Ramsden's Machine. has ten radii, each being supported by edge-bars, as represented in fig. 3. These bars and radii are connected by the circular ring B, 24 inches in diameter and three deep; and for greater strength, the whole is cast in one piece in bell-metal.

"As the whole weight of the wheel A rests on its ring B, the edge-bars are deepest where they join it; and from thence their depth diminishes, both towards the centre and the circumference, as represented in fig. 3.

"The surface of the wheel A was worked very even and flat, and its circumference turned true. The ring C, of fine brass, was fitted very exactly on the circumference of the wheel; and was fastened thereon with screws, which, after being screwed as tight as possible, were well rivetted. The face of a large chuck being turned very true and flat in the lathe, the flattened surface A of the wheel was fastened against it with hold-fasts; and the two surfaces and circumferences of the ring C, a hole through the centre and the plane part round (b) it, and the lower edge of the ring B, were turned at the same time.

"D is a piece of hard bell-metal, having the hole, which receives the steel arbor d, made very straight and true. This bell-metal was turned very true on an arbor; and the face, which rests on the wheel at b, was turned very flat, so that the steel arbor d might stand perpendicular to the plane of the wheel: this bell metal was fastened to the wheel by six steel screws l.

"A brass socket Z is fastened on the centre of the mahogany stand, and receives the lower part of the bell-metal piece D, being made to touch the bell-metal in a narrow part near the mouth, to prevent any obliquity of the wheel from bending the arbor: good fitting is by no means necessary here; since any shake in this socket will produce no bad effect, as will appear hereafter when we describe the cutting frame.

"The wheel was then put on its stand, the lower edge of the ring B resting on the circumference of three conical friction-pulleys W, to facilitate its motion round its centre. The axis of one of these pulleys is in a line joining the centre of the wheel and the middle of the endless screw, and the other two placed so as to be at equal distances from each other.

"F is a block of wood strongly fastened to one of the legs of the stand; the piece g is screwed to the upper side of the block, and has half holes, in which the transverse axis h turns: the half holes are kept together by the screws i.

"The lower extremity of the conical pillar P terminates in a cylindrical steel-pin k, which passes through and turns in the transverse axis h, and is confined by a check and screw.

"To the upper end of the conical pillar is fastened the frame G, in which the endless screw turns: the pivots of the screw are formed in the manner of two frustums of cones joined by a cylinder, as represented at X. These pivots are confined between half poles, which press only on the conical parts, and do not touch the cylindric parts: the half holes are kept together by screws a, which may be tightened at any time, to prevent the screw from shaking in the frame.

"On the screw-arbor is a small wheel of brass K, having its outside edge divided into 60 parts, and num-

bered at every 6th division with 1, 2, &c. to 10. The motion of this wheel is shown by the index y on the screw-frame G.

"H represents a part of the stand, having a parallel slit in the direction towards the centre of the wheel, large enough to receive the upper part of the conical brass pillar P, which carries the screw and its frame: and as the resistance, when the wheel is moved by the endless screw, is against that side of the slit H which is towards the left hand, that side of the slit is faced with brass, and the pillar is pressed against it by a steel spring on the opposite side: by this means the pillar is strongly supported laterally, and yet the screw may be easily pressed from or against the circumference of the wheel, and the pillar will turn freely on its axis to take any direction given it by the frame L.

"At each corner of the piece I are screws n of Fig. 4 tempered steel, having polished conical points: two of them turn in conical holes in the screw frame near o, and the points of the other two screws turn in holes in the piece Q; the screws p are of steel, which being tightened, prevent the conical pointed screws from unturning when the frame is moved.

"L is a brass frame, which serves to connect the endless screw, its frame, &c. with the centre of the wheel: each arm of this frame is terminated by a steel screw, that may be passed through any of the holes q in the piece Q, as the thickness of work to be divided on the wheel may require, and are fastened by the finger-nuts r.

"At the other end of this frame is a flat piece of tempered steel b, wherein is an angular notch: when the endless screw is pressed against the teeth on the circumference of the wheel, which may be done by turning the finger-screw S, to press against the spring t, this notch embraces and presses against the steel arbor d. This end of the frame may be raised or depressed by moving the prismatic slide u, which may be fixed at any height by the four steel screws v.

"The bottom of this slide has a notch k, whose plane is parallel to the endless screw; and by the point of the arbor d resting in this notch, this end of the frame is prevented from tilting. The screw S is prevented from unturning, by tightening the finger-nut w.

"The teeth on the circumference of the wheel were cut by the following method:

"Having considered what number of teeth on the circumference would be most convenient, which in this engine is 2160, or 360 multiplied by 6, I made two screws of the same dimensions, of tempered steel, in the manner hereafter described, the interval between the threads being such as I knew by calculation would come within the limits of what might be turned off the circumference of the wheel: one of the screws, which was intended for ratching or cutting the teeth, was notched across the threads, so that the screw, when pressed against the edge of the wheel and turned round, cut in the manner of a saw. Then having a segment of a circle a little greater than 60 degrees, of about the same radius with the wheel, and the circumference made true, from a very fine centre, I described an arch near the edge, and set off the chord of 60 degrees on this arch. This segment was put in the place of the wheel, the edge of it was ratched, and the number of revolutions

Ramsden's revolutions and parts of the screw contained between machine. the interval of the 60 degrees were counted. The radius was corrected in the proportion of 360 revolutions, which ought to have been in 60 degrees, to the number actually found; and the radius, so corrected, was taken in a pair of beam-compasses: while the wheel was on the lathe, one foot of the compasses was put in the centre, and with the other a circle was described on the ring; then half the depth of the threads of the screw being taken in dividers, was set from this circle outwards, and another circle was described cutting this point; a hollow was then turned on the edge of the wheel of the same curvature as that of the screw at the bottom of the threads: the bottom of this hollow was turned to the same radius or distance from the centre of the wheel, as the outward of the two circles before mentioned.

Fig. 3. "The wheel was now taken off the lathe; and the bell-metal piece D was screwed on as before directed, which after this ought not to be removed.

Fig. 1, 2, 3. "From a very exact centre a circle was described on the ring C, about four-tenths of an inch within where the bottom of the teeth would come. This circle was divided with the greatest exactness I was capable of, first into five parts, and each of these into three. These parts were then bisected four times: (that is to say) supposing the whole circumference of the wheel to contain 2160 teeth, this being divided into five parts, each would contain 432 teeth; which being divided into three parts, each of them would contain 144; and this space bisected four times would give 72, 36, 18, and 9: therefore each of the last divisions would contain nine teeth. But, as I was apprehensive some error might arise from quinquesection and trisection; in order to examine the accuracy of the divisions, I described another circle on the ring C, one tenth of an inch within the former, and divided it by continual bisections, as 2160, 1080, 540, 270, 135, 67½, and 33¼; and as the fixed wire (to be described presently) crossed both the circles, I could examine their agreement at every 135 revolutions; (after ratching, could examine it at every 33¼): but, not finding any sensible difference between the two sets of divisions, I, for ratching, made choice of the former; and, as the coincidence of the fixed wire with an intersection could be more exactly determined than with a dot or division, I therefore made use of intersection in both circles before described.

Fig. 4. "The arms of the frame L were connected by a thin piece of brass of three-fourths of an inch broad, having a hole in the middle of four-tenths of an inch in diameter; across this hole a silver wire was fixed exactly in a line to the centre of the wheel; the coincidence of this wire with the intersections was examined by a lens seven-tenths of an inch focus, fixed in a tube which was attached to one of the arms L (A). Now a handle or winch being fixed on the end of the screw, the division marked on the end of the screw, the division marked 10 on the circle K was set to its index, and, by means of a clamp and adjusting screw for that purpose, the intersection marked 1 on the circle C was set exactly to

coincide with the fixed wire; the screw was then carefully pressed against the circumference of the wheel, by turning the finger-screw S; then, removing the clamp, I turned the screw by its handle nine revolutions, till the intersection marked 240 came nearly to the wire; then, unturning the finger-screw S, I released the screw from the wheel, and turned the wheel back till the intersection marked 2 exactly coincided with the wire, and, by means of the clamp before mentioned, the division 10 on the circle being set to its index, the screw was pressed against the edge of the wheel by the finger-screw S; the clamps were removed, and the screw turned nine revolutions till the intersection marked 1 nearly coincided with the fixed wire; the screw was released from the wheel by unturning the finger-screw S, as before, the wheel was turned back till the intersection 3 coincided with the fixed wire; the division 10 on the circle being set to its index, the screw was pressed against the wheel as before, and the screw was turned nine revolutions, till the intersection 2 nearly coincided with the fixed wire, and the screw was released; and I proceeded in this manner till the teeth were marked round the whole circumference of the wheel. This was repeated three times round, to make the impression of the screw deeper. I then ratched the wheel round continually in the same direction without ever disengaging the screw; and, in ratching the wheel about 300 times round, the teeth were finished.

"Now it is evident, if the circumference of the wheel was even one tooth or ten minutes greater than the screw would require, this error would in the first instance be reduced to $\backslash frac\{1\}\{240\}$ part of a revolution, or two seconds and a half; and these errors or inequalities of the teeth were equally distributed round the wheel at the distance of nine teeth from each other. Now, as the screw in ratching had continually hold of several teeth at the same time, and, these constantly changing, the above-mentioned inequalities soon corrected themselves, and the teeth were reduced to a perfect equality. The piece of brass which carries the wire was now taken away, and the cutting screw was also removed, and a plain one (hereafter described) put in its place: on one end of the screw is a small brass circle, having its edge divided into 60 equal parts, and numbered at every sixth division, as before mentioned. On the other end of the screw is a ratchet-wheel C, having 60 teeth, covered by the hollowed circle d, which carries two Fig. 5. clicks that catch upon the opposite sides of the ratchet when the screw is to be moved forwards. The cylinder S turns on a strong steel arbor F, which passes through and is firmly screwed to the piece Y: this piece, for greater firmness, is attached to the screw-frame G by the braces v; a spiral groove or thread Fig. 4. is cut on the outside of the cylinder S, which serves both for holding the string, and also giving motion to the lever J on its centre by means of a steel tooth n, that works between the threads of the spiral. To the lever is attached a strong steel pin m, on which a brass socket r turns: this socket passes through a slit in

Ramsden's in the piece p, and may be tightened in any part of Machine. the slit by the finger-nut f: this piece serves to regulate the number of revolutions of the screw for each tread of the treadle R.

Fig. 1. "T is a brass box containing a spiral string; a strong gut is fastened and turned three or four times round the circumference of this box, the gut then passes several times round the cylinder S, and from thence down to the treadle R. Now, when the treadle is pressed down, the string pulls the cylinder S round its axis, and the clicks catching hold of the teeth on the ratchet carry the screw round with it, till, by the tooth n working in the spiral groove, the lever J is brought near the wheel d, and the cylinder stopped by the screw-head x striking on the top of the lever J; at the same time the spring is wound up by the other end of the gut passing round the box T. Now, when the foot is taken off the treadle, the spring unbending itself pulls back the cylinder, the clicks leaving the ratchet and screw at rest till the piece t strikes on the end of the piece p: the number of revolutions of the screw at each tread is limited by the number of revolutions the cylinder is allowed to turn back before the stop strikes on the piece p.

Fig. 1. & 4. "When the endless screw was moved round its axis with a considerable velocity, it would continue that motion a little after the cylinder S was stopped: to prevent this, the angular lever x was made; that when the lever J comes near to stop the screw x, it, by a small chamfer, presses down the piece x of the angular lever; this brings the other end x of the same lever forwards, and stops the endless screw by the steel pin μ striking upon the top of it; the foot of the lever is raised again by a small spring pressing on the brace v.

Fig. 1, 2, 6. "D, two clamps, connected by the piece x, slide one on each arm of the frame L, and may be fixed at pleasure by the four finger-screws e, which press against steel springs to avoid spoiling the arms: the piece q is made to turn without shake between two conical pointed screws f, which are prevented from unturning by tightening the finger-nuts N.

Fig. 6. "The piece M is made to turn on the piece q by the conical pointed screws f resting in the hollow centers e.

"As there is frequent occasion to cut divisions on inclined planes, for that purpose the piece γ, in which the tracer is fixed, has a conical axis at each end, which turns in half holes: when the tracer is set to any inclination, it may be fixed there by tightening the steel screws β.

"Fig. 9. represents this engine of its full dimensions seen from one side.

"Fig. 8. the upper side of the same as seen from above.

"A represents a triangular bar of steel, to which the triangular holes in the pieces B and C are accurately fitted, and may be fixed on any part of the bar by the screws D.

"E is a piece of steel whereon the screw is intended to be cut; which, after being hardened and tempered, has its pivots turned in the form of two frustums of cones, as represented in the drawing of the dividing engine (fig. 5.). These pivots were exactly fitted to the

half holes F and T, which were kept together by the screw Z. Ramsden's Machine Ramsden's

"H represents a screw of untempered steel, having a pivot I, which turns in the hole K. At the other end of the screw is a hollow centre, which receives the hardened conical point of the steel pin M. When this point is sufficiently pressed against the screw, to prevent its shaking, the steel pin may be fixed by tightening the screws Y.

"N is a cylindric nut, moveable on the screw H; which, to prevent any shake, may be tightened by the screws O. This nut is connected with the saddle-piece P by means of the intermediate universal joint W, through which the arbor of the screw H passes. A front view of this piece, with the section across the screw arbor, is represented at X. This joint is connected with the nut by means of two steel slips S, which turn on pins between the cheeks T on the nut N. The other ends of these slips S turn in like manner on pins a. One axis of this joint turns in a hole in the cock b, which is fixed to the saddle-piece; and the other turns in a hole d, made for that purpose in the same piece on which the cock b is fixed. By this means, when the screw is turned round, the saddle-piece will slide uniformly along the triangular bar A.

"K is a small triangular bar of well-tempered steel, which slides in a groove on the saddle-piece P. The point of this bar or cutter is formed to the shape of the thread intended to be cut on the endless screw. When the cutter is set to take proper hold of the intended screw, it may be fixed by tightening the screw c, which presses the two pieces of brass G upon it.

"Having measured the circumference of the dividing-wheel, I found it would require a screw about one thread in a hundred coarser than the guide-screw H. The wheels on the guide-screw arbor H, and that on the steel E, on which the screw was to be cut, were proportioned to each other to produce that effect, by giving the wheel L 198 teeth, and the wheel Q 200. These wheels communicated with each other by means of the intermediate wheel R, which also served to give the threads on the two screws the same direction.

"The saddle-piece P is confined on the bar A by means of the pieces g, and may be made to slide with a proper degree of tightness by the screws n." See DIVIDING INSTRUMENTS, SUPPLEMENT.

For Ramsden's equatorial or portable observatory, see OFFICE, N^o 89. and ASTRONOMY, N^o 364. See also a long account of an equatorial instrument made by Mr Ramsden by the direction of Sir George Shuckburgh in the Philosophical Transactions for 1793, art. x. p. 67. In this instrument the circle of declinations is four feet in diameter, and may be observed nearly to a second. The glass is placed between six pillars, which form the axis of the machine, and turn round by two pivots placed on two blocks of stone. See also BAROMETER.