is an apparatus so necessary to the chemist, that every contrivance to render it more convenient, or to lessen the expense of it, must contribute greatly to the advancement of science. The abilities of Moreau alias Gayton, and the success with which he has prosecuted the study of chemistry, are well known; and therefore his different methods of saving time and expense in making chemical experiments must be worthy of the notice of younger chemists.

In the second volume of the Memoirs of the Ancient Academy of Dijon, we have a description by him of a box containing a kind of portable laboratory, composed of a lamp with three wicks, clipped in the figure of an equilateral triangle, to form an internal current of air, with supports for the different vessels of digestion, dilution, evaporation, &c. He made a solution of silver with common aqua fortis and the metal in an alloyed state, which answered very well as a re-agent, without having occasion for any other utensils but this box and apothecary's phials, which are everywhere to be found.

This apparatus, however, was confined in its application, and he soon thought of improving it. He constructed a lamp, on the principles of Argand, with three concentric circular wicks, each having an interior and exterior current of air. The effect surpassed his expectations with regard to the intensity of the heat; but it was difficult to prevent the destruction of the hard folder round the wicks; and the glass retorts were frequently melted at the bottom, and disfigured. It was attended with other inconveniences, and the quantity of oil consumed was great.

A short time afterwards, it occurred to him to substitute, instead of the glass chimney of Argand's lamp, a cylinder of copper with an indented part or ledge a few millimetres (see Revolution, Encycl. n° 184.) above the flame, to perform the office of the indented chimney of glass, and by that means to render it practicable to raise the wick to a certain height without smoking. This cylinder has three branches like a chaffing-dish. By this apparatus two or three decilitres of water (about half an English wine pint) may be brought to boil in a copper or glass vessel in about five or seven minutes. It has served for a number of operations; but it was not till after he had observed the degree of heat obtained from the lamp in its ordinary state, and particularly since he had substituted, instead of the metallic tube, a chimney of glass cut off at the length of three centimetres. centimetres (rather more than one English inch) above the contraction, that he perceived all the advantages it was capable of affording; and that by means of a moveable support for the reception of the different vessels, which may be fixed at pleasure by a thumb-screw, this lamp furnaces, at the same time that it gives light, and consequently without any additional expense, may with facility be used for almost every one of the operations of chemistry; such as digestions, solutions, crystallizations, concentrations; the rectification of acids; distillations on the sand-bath, or by the naked fire; incinerations of the most refractory residues; analyses with the pneumatic apparatus, or of minerals by the saline fusion, &c. "I have not (says he) hitherto met with any exception but for complete vitrifications and capping; for even the distillations to dryness may be performed with some precautions, such as that of transferring the matter into a small retort blown by the chemist's lamp, and placing its bottom on a little sand-bath in a thin metallic dish." The support here mentioned is simply a copper ring eight centimetres (3.15 inches) in diameter, which is raised or lowered by sliding on a stem of the same metal. Nothing more was required but to adapt it to the square iron stem which passes through the reservoir of the lamp. The connection is made by a piece of wood, in order that less of the heat might be dispersed. As the lamp itself is capable of being moved on its stem, it is easy to bring it nearer or remove it at pleasure from the vessels, which remain fixed; a circumstance which, independent of the elevation or depression of the wick, affords the means of heating the retorts by degrees, of moderating or suppressing the fire instantly, or of maintaining it for several hours at a constant or determinate intensity, from the almost insensible evaporation of crystallizable solutions to the ebullition of acids; properties never possessed by the athanor, of which chemists have boasted so much. The advantage of these will be properly valued by those operators who know that the most experienced and the most attentive chemists meet with frequent accidents, by which both their vessels and the products of their operations are lost for want of power in the management of the fire."

For the analysis of stones, such as the crystals of tin, the shortened chimney of glass is to be used; and the process is to be begun by placing the mixture in a capsule of platinum or silver 2½ inches in diameter. This capsule is to be placed on the support, and the heat regulated in such a manner, that ebullition shall take place without throwing any portion of the matter out of the vessel. As soon as its contents are perfectly dry, they are to be transferred into a very thin crucible of platinum, of which the weight is about 252½ grains English, and its diameter one inch and three-fourths. This crucible rests on a small support of iron-wire, which serves to contract the ring; and the wick being at its greatest elevation, with the ring lowered to the distance of 9½ inches from the upper rim of the chimney, Guyton produced, in less than twenty minutes, the saline fusion to such a degree, that from the commencement of the operation the decomposition proceeded as far as to 0.70 of the mineral. The same apparatus, that is to say, with the shortened chimney, serves for oxidations, incinerations, torrefactions, and distillations to dryness.

In such operations as require a less heat, he leaves the lamp with its large chimney absolutely in the same state as when it is used for illumination; and by raising and lowering either the ring which supports the vessel, or the body of the lamp if the vessels be fixed in communication with others, he graduates the heat at pleasure. Vinegar distills without interruption at 2½ inches English from the upper termination of the chimney, that is to say, 7½ inches English from the flame. Water is made to boil in eight minutes, at the same height, in a glass vessel containing one wine pint English, and is uniformly maintained at the distance of 8½ inches from the flame.

"I must not in this place (says our author) omit to mention a slight observation which this process has afforded, because it may lead to useful applications, and tends to point out one great advantage of this method of operating; namely, that an infinity of circumstances may be perceived, which might not even be suspected when the whole process is carried on within a furnace. I have remarked, as did likewise several of my colleagues who were then present, that a column of bubbles constantly rose from a fixed point of the retort on one side of the bottom. We were of opinion, that some particle of matter was in that place incorporated with the glass, which had a different capacity for heat from that of the rest of the glass. In order to verify this conjecture, I endeavoured the following day to distil the same quantity of the same water in the same retort, after having introduced a button of cupelled silver, weighing nine decigrammes (20½ grams). At the commencement of the operation there was a small stream of bubbles from the same point as before; but a short time afterwards, and during the whole remaining time of operating, the largest and most incessant stream of bubbles rose from the circumference of the button, which was often displaced by the motion; and in proportion to the time the product of the distillation was sensibly greater. Whence we may conclude, that metallic wires or rods, distributed through a mass of water required to be kept in a state of ebullition, and placed a little below its surface, would produce, without any greater expense of fuel, nearly the same effect as those cylinders filled with ignited matter which are made to pass through the boilers."

We have related this fact, in Guyton's own words, or at least in a faithful translation of them; and we are far from calling it in question, for it is a fact which has been often observed; but we think his inference from it too hastily drawn. It is not conceivable that heat can be more rapidly conveyed through a mass of liquid by the conducting power of metal, than by a free circulation; but we agree with what seems to be Mr Nicholson's opinion *, that the thin stratum of water beneath the button becomes more suddenly and violently elastic again than elsewhere, and therefore rises regularly to the surface. The whole of this phenomenon the reader will find explained in our article Steam (Encycl.), p. 10.

But this is a digression.

We return therefore to Guyton's laboratory, of which the reader will form a distinct notion from plate XXXIII. where fig. 1 represents the whole apparatus ready mounted for distillation, with the tube of safety and a pneumatic receiver. A is the body or reservoir of the usual lamp of Argand, with its shade and glass chimney. The lamp may be raised or lowered at pleasure by means of the thumb screw B, and the wick rises and... and falls by the motion of the small toothed wheel placed over the waffle cup. This construction is most convenient, because it affords the facility of altering the position of the flame with regard to the vessels, which remain fixed; and the troublesome management of bended wires above the flame for the support of the vessels is avoided, at the same time that the flame itself can be brought nearer to the matter on which it is intended to act. D, a support consisting of a round stem of brass, formed of two pieces which screw together at about two thirds of its height. Upon this the circular ring E, the arm F, and the nut G slide, and are fixable each by its respective thumb-screw. The arm also carries a moveable piece H, which serves to suspend the vessels in a convenient situation, or to secure their position. The whole support is attached to the square iron stem of the lamp by a piece of hard wood I, which may be fixed at any required situation by its screw. K represents a stand for the receivers. Its moveable tablet L is fixed at any required elevation by the wooden screw M. The piece which forms the foot of this stand is fixed on the board N; but its relative position with regard to the lamp may be changed by sliding the foot of the latter between the pieces OO. P, another stand, for the pneumatic trough. It is raised or lowered, and fixed to its place, by a strong wooden screw. Q. R is a tube of safety, or reversed syphon, which serves, in a great measure, to prevent the bad effects of having the vessels either perfectly closed, or perfectly open. Suppose the upper bell-shaped vessel to be nearly of the same magnitude as the bulb at the lower end of the tube, and that a quantity of water, or other suitable fluid, somewhat less than the contents of that vessel, be poured into the apparatus: In this situation, if the elasticity of the contents of the vessel be less than that of the external air, the fluid will descend into the bulb, and atmospheric air will follow and pass through the fluid into the vessel; but, on the contrary, if the elasticity of the contents be greater, the fluid will be either sustained in the tube, or driven into the bell-shaped vessel; and if the force be strong enough, the gaseous matter will pass through the fluid, and in part escape.

Fig. 2. Shows the lamp furnace disposed to produce the saline fusion; the chimney of glass shortened; the support D turned down; the capsule of platinum or silver S placed on the ring very near the flame.

Fig. 3. The same part of the apparatus, in which, instead of the capsule, a very thin and small crucible of platinum T is substituted, and rests upon a triangle of iron wire placed on the ring.

Fig. 4. Exhibits the plan of this last disposition.