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much greater. If æther, for instance, could be placed in the same condi. tions of expansion as the liquefied gas, a much greater frigorific effect would be obtained than by liquified carbonic acid. To accomplish this object it is necessary to render æther explosive, which is easily effected by mixing æther with liquid carbonic acid. In this intimate combination of two liquids which dissolve one another in every proportion, the æther ceases to be a liquid permanent under the pressure of the atmosphere; it becomes expansive similar to a liquefied gas, at the same time preserving its properties as a vapour; that is to say, its conductibility and capacity for caloric.

The effects produced by a tube filled with explosive æther are remarkable; a few seconds were sufficient to congeal 722 grains of mercury in a glass vessel. On exposing the finger to the jet which escapes, the sensation is intolerable, and seems to extend much further than the point of contact

, M. Thilorier intends to replace æther by sulphuret of carbon; and it is probable that the effects obtained will be still more powerful.

Annales de Chimie et de Phys and Lond. and Ed. Phil. Mag. Solidification of Carbonic Acid. M. Thilorier has read to the Academy of Sciences a memoir containing an account of the means by which he reddered carbonic acid solid; and he also gave some details respecting liquid carbonic acid.

He finds the finds the specific gravity of the liquid acid to be .83, water being 1.; it dissolves in all proportions in alcohol and æther: potassium de composes it, but the common metals do not. A jet of carbonic acid, directed upon a spirit thermometer, caused it to fall 194° below zero Fabr. The cold would have been still greater if the bulb of the thermometer could have been entirely covered by the jet.

The solidification of carbonic acid was effected in the following manner. a jet of liquid carbonic acid was received in a glass vial; the expansion of which it undergoes is about 400 times its original volume, and by this so intense a cold is produced, that one part of the carbonic acid congeals in a white powder and adheres to the glass. This powder exists for some minutes, and without any pressure. if the finger be placed in solid carbonic acid, the heat converts it into gas, the expansion of which repels the finger. A few grains of this powder, closed in a vessel, soon expelled the cork.

Solid carbonic acid contains a little water, which is doubtless derived from the moisture of the air. In order, however, to remove all doubts, it would be necessary to get rid of the hygrometric moisture, both of the air and of the vessels, because it might be supposed that this water facilitates the conge. lation of the acid, as is the case with chlorine.

As to the temperature of this congelation, it was determined by using a spirit thermometer graduated to 1870 below zero, to which about 44° must be added for the tube of the thermometer which could not be cooled, so that the cold observed was not less than 231°*.

These experiments were verified by commissioners, among whom were MM, Thenard and Dulong.

Journal de Chim. Med., tome ii. p. 3, and Lond. and Edin. Philos. Mag. Water of the Elton, Dead, and Caspian Seas.f The Elton sea lies to the east of the Volga, 274 versts (181} miles), south from Saratov. Its greatest diameter, from east to west, is 17 (11} miles), and its smallest diameter 13 versts, (83 miles).

• These are lower temperatures than have ever before been artificially produced, and lower also, we believe, than any which have yet been observed in nature.--ED.

† Poggendorff's Annalen xxiv. 169.

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The water of the Eltop sea resembles that of the Dead sea, but the latter
has a less specific gravity, and a smaller quantity of solid constituents. The
quantity of salt diminishes when the Jordan is overflowed. Gay Lussac
allowed the water to cool to 19° F. without separating any salt; while
Klaproth states, that at the bottom of the flask which contained the speci-
med which he examined, crystals of common salt were deposited, which
soon disappeared. The specific gravity of the Dead Sea varies, and the
reason is obvious. Macquer, Lavoisier, and Sage found it 1.240; Marcet
and Tennant 1.211; Klaproth 1.245; Gay Lussac at 62o.6, 1.2283; Hermb-
stadt at 60° 1.240. The proportion of ingredients also varies. Gay Lussac
found them 26. 24 per cent.; consisting of chlorides of sodium, calcium, mag-
Desium, and potassium, and traces of gypsum, differing from that of the
Elton Sea by the absence of Epsom salt, and the presence of chloride of
calcium.

According to Marcet, the specific gravity of the water of the Sea of
Urmia is 1.16507, and its constituents 22.3 per cent, consisting of common
salt, Epsom salt, and sulphate of soda. The saline contents of Urmia and

the Dead Sea are, therefore, inferior to those of the Elton Sea. Rose bas appropriated all the sulphuric acid to the magnesia, because he has found that when common salt and Epsom salt are dissolved in a sufficient quantity of water and evaporated in a summer heat, the two salts separate; and when much common salt is dissolved along with a small quantity of Epsom salt, a part of the common salt separates first, and then the Epsom salt, while common salt remains in solution; as by the heat of summer, Epsom salt is less soluble than common salt. When the temperature is raised abore 122. F. or sunk to zero, in both cases, glauber salt and chloride of magne. sium are formed.

Rose found the specific gravity of water brought from the Caspian Sea 75 versts from the islands formed by the Volga, at 541°, 1.0013; and its contents, Chloride of sodium,

.754 Sulphate of soda,

.036 Sulphate of lime,

.406 Bicarbonate of lime,

.018 Bicarbonate of magnesia,

.440 Water with a small quantity of organic matter,

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Record Gen. Sc. February. Rationale of cold produced by sulphate of Soda and muriatic acid, Doct. Kane makes the following statement in a paper on the action of moriatic acid on the sulphates. "It has been long known that Glauber's salt treated with muriatic acid constitutes a powerful freezing mixture, the tbeory of which is at once explained by the results of the experiment. When sulphate of soda is dissolved in liquid muriatic acid there are formed bisul. phate of soda and chloride of sodium, and as the former salt crystalizes with only four atoms of water, the remaining quantity of the water of crystalization of the Glauber's salt, is disengaged to the amount of sixteen atoms." “This large quantity of water suddenly separated from a state of combination in which it had been solid, produces, by its absorption of caloric of liquidity, the frigorific property." Lond. and Edin. Philos. Mag. May.

Progress of Practical and Theoretical Mechanics and Chemistry.

Description of a new Detached Pendulum Escapement, invented by Alexan

der Witherspoon, watch-maker, Tranent.* A, is the pendulum rod, represented as having nearly reached the limit of its vibration to the left, and as about to touch the small friction roller attached to the arm C D of the impeller B C D E. The upper part of the pendulum rod is broken off to show the axis B, concentric with the axis of motion of the pendulum itself, on which the impeller turns. The two axes coinciding in direction, no rubbing ought to take place though there were no friction roller at D; the roller is merely placed there for the purpose of preventing the bad effects of any small error in the adjustment. In the drawing, the weight of the impeller is represented as sustained, through the intervention of the slender spring E F, by the lifting pin F, which is placed near the centre of

* Read before the Society of Arts, 13th April, 1831.

H

the scapement wheel; this wheel itself being prevented from advancing by the opposition of the detent to the detaining tooth H. The end of the spring E F is furcated, the pin resting in the bottom of the notch, and keeping the spring bent upwards from its natural position by a distance rather more than the minute diameter of the pin.

The oscillation of the pendulum is so nearly completed, that, when finished, the impeller B C D E may be lift.

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B ed till the extremity of the spring just escapes from the pin F, and takes up a position a little to the left of its present one. The whole weight of the impeller now rests upon the pendulum; but when the pendulum begins to retire, the extremity of the spring is not arrested by the pin F, but passes close by it, directing its motion towards the pin G.

The impeller continues to press against the pendulum rod, and increases its mo

D mentum until the arm B E reaches a pin at L, projected from the branch of the detent HKL. After this the penduluin continues its oscillation uninterrupted.

The detent turns upon an axis at K, so that the pressure of the impeller upon the pin L elevates the detent, and allows the detaining tooth H to pass forward.

Just at this moment the second lifting pin G is entangled between the sides of the notch in the extremity of the spring E F; the motion of the wheel, therefore, again elevates the impeller, the rise of which allows the detent to descend upon the stop N and await the arrival of the second detaining tooth I, whose arrest is announced by a distinct beat.

The whole of the escapement has now assumed a position exactly analogous to that which it had at first, and awaits the approach of the pendulum, to solicit anew its maintaining power.

During the whole of this action the pendulum is never connected with the train of wheels. The only body which acts upon it is the impeller, and this communicates to it the impulse which is generated by a descent of a constant weight through a determinate distance. The lightness of the parts renders oil either on the axis B or on the pin F unnecessary, so that this action is entirely freed from any error which might have arisen from changes in the adhesiveness of oil. In order to solicit the impulsion, the pendulum has to raise the impeller through a distance determined by the thickness of the pin F, and has to overcome the friction of the spring against that pin. But the diameter of the pin is so small and the flexure of the spring so slight, that the errors caused by them must be exceedingly small, especially when we consider that they are not liable to any variation. The unlocking of the detent H, instead of being performed by the pendulam, is effected by the impeller; so that, however variable may be the maintaining force, provided it is never so small as to be unable to raise the impeller, nor so great as to prevent the unlocking of the detent, the going of the clock can never be in the slightest degree affected.

When the pendulum rod reaches the friction-roller, it is moving with a VOL. XVIII.No, 3.-SEPTEMBER, 1836.

18

very small velocity, since it is almost at the limit of its oscillation, so that nothing analogous to the blow of the common 'scapements takes place; and even the sudden removal of the pressure of the impeller, when the arm reaches the pin L, can hardly excite any tremour in the pendulum.

In almost all delicate escapements, high finish in the rubbing surfaces and great accuracy in the workmanship, are absolutely essential to good going. In every case the advantage of careful execution cannot fail to be felt; but in this escapement that advantage is by no means great. The execution of the train is almost a matter of indifference; and even in the most vital part, though the distances of the detaining teeth were inaccurately laid off, the errors would occur at every revolution of the escapement wheel, and their effects on the going would be generated and destroyed in the same period, so that the daily or hourly rate could not be affected.

The motion of the train resembles that of a perfect dead-beat, although the escapement certainly partakes of the nature of the recoil, since the unhooking of the spring is only effected after a slight elevation of the impeller, The beat is made only at each second oscillation, so that, in order to beat seconds, a half second pendulum must be used. In escapements which beat at each vibration, it is difficult to have two consecutive intervals esactly equal,—the one being less, and the other as much more than an exact second; but when the beat is given only on one side, no such inequality can exist.

The parts of the impeller are liable to expansion by heat, but the effects of this can easily be obviated by extending an arm made of some expansive metal such as zinc, on the other side of the axis B, while the branches represented in the figure are made of glass. This arm also will allow a weight to be slid along it so as to regulate the intensity of the impulse.

When the spring is released from the pin F, it does not merely assume its position of rest, bul continues for a moment to vibrate on each side of it

. As there might appear to be some risk of its catching again the same pin, a damper has been put on to diminish these oscillations; but, as in some other escapements which I have constructed on the same principle, it was not found necessary; it has been omitted in the drawing. I need hardly point out that the number of lifting pins is pot limited to four. Jameson's Journal.

Capillary Tubes in Metal. The sum of five pounds was presented to Mr. J. Roberts, 64 Queen Street, Cheapside, for his method of subdividing a pipe into capillary tubes; a specimen of which has been placed in the Society's Repository. The thanks of the Society were voted to Hen. Wilkinson, Esq. Pall Mall, for his method of producing a ring of capillary tubes. For gas-burners, for the safe combustion of mixtures of oxygen and hydrogen, and for other purposes, it is often desirable to divide the end of the discharge.pipe into fine capillary tubes, of the depth of half an inch or more. It is difficult and expensive to bore such apertures in a piece of solid metal, and it is hardly possible to be executed at all if the apertures are required to be of very small diameter.

Mr. Roberts very ingeniously and expeditiously subdivides the end of a metal pipe into small tubes of any required depth, by means of pinion-wire. Pinion-wire is made by taking a cylindrical wire of soft steel, and passing it through a draw-plate of such a figure as to form on its surface deep grooves in the direction of radii to the axis of the wire: the ribs which separate these grooves from one another may be considered as leaves or teeth, and of such wire, when cut into proper lengths, are made the pinions used by watchmakers. Hence arises the name by which this wire is commonly known

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