bines a copious discussion of the opinions of preceding inquirers, appears to have ascertained the cause of those anomalous statements. It exists in the particular nature of the medium by which the rays of light are decomposed; a circumstance so little regarded, that few experimenters have even deemed it necessary to record the material of their prism. The following is a summary of his results.

In every part of the prismatic spectrum there is a perceptible elevation of temperature, and this is uniformly least in the outermost edge of the violet. From the violet it gradually increases, as we proceed through the blue and green into the yellow and red. In some prisms it attains a maximum in the yellow, as, for example, in those filled with water, alcohol, or oil of turpentine. In others, as in those filled with a transparent solution of sal ammoniac and corrosive sublimate, it attains a maximum in the orange. Prisms of crown glass and of common white glass have the maximum of temperature in the centre of the red; others, which appeared to contain lead, have the maximum in the limit of the red. Prisms of flint glass have the maximum beyond the red. In all prisms, without exception, the temperature regularly diminishes from beyond the red; but it still continues perceptible at a distance of several inches from the extremest limit of that side of the visible spectrum-Schweigger's Neues Jour nal, vol. x. p. 129.

CONVERSION OF HONEY

INTO SUGAR.

THE Jews in Moldavia and Ukrane have a method of making honey into a hard and white sugar, which is employed by the distillers of Dantzic to make their liqueurs. The process consists in exposing the honey to the frost during three weeks, sheltered from the sun and snow in a vase of some material which is a bad conductor of caloric. The honey does not freeze, but becomes transparent and hard as sugar.Hanoverisches Magazin.

ATTRACTION OF PARTICLES OF GASES.

Woolwich, Sept.3.

THE study of any science, particularly that of chemistry, is pursued with more facility and pleasure, the more clearly the facts connected with it are stated and the phenomena it presents are more accurately viewed. To accomplish this being one principal design of your publication, encourages me to offer the following observations.

All the chemical authors which I have read, when treating of the three forms of matter (solid, liquid, and aeriform,) assert that the gaseous is that state in which the attractive force is entirely overcome, and the repulsive has gained the ascendency, or that the particles of gases are mutually repellent.

Now, Sir, in first reading these assertions, I was very much perplexed, for I cannot conceive how substances can exist while their particles repel each other; indeed, were this the case, I should imagine that the moment substances assumed this form, they would fly off in all directions, and constitute an indiscriminate and heterogeneous mixture with the atmosphere and each other; consequently we should not be able to obtain any such thing as a simple gas.

But from a more minute consideration, I think a very cursory view of the subject will prove that every species of attraction exists in the gaseous as well as any other state, e. g. take two volumes of carbonic acid gas, pour them into an open vessel, it will displace the atmospheric air, combine, and form one volume equal in bulk to both; it may also be allowed to remain in the vessel for a considerable time without mixing with the atmosphere: its particles, therefore, possess sufficient attraction to each other to cause them to unite, and preserve their identity after they have united; and this experiment may be performed with any other gases, where the difference of specific gravity is sufficient, and no particular chemical affinity exists;

and this I consider the attraction of aggregation, in the strictest sense of the word.

It were unnecessary to attempt to prove that the attraction of gravitation or combination exists in the particles of gases, as that is evident from their weight, and this sufficiently obvious from the numerous instances of gaseous combination, which all your readers must be acquainted with.

If you consider these remarks deserving a place in your useful work, they are at your service; and by inserting them you will oblige

Your humble servant
and constant reader,
J. ALWIN.

To FREEZE ONE LIQUID AND
BOIL ANOTHER
SAME MEANS.

BY THE

ELECTRICITY BY WATER FREEZING.

ing hot and cold with the same breath. The manner in which heat is distributed has taught us that in this instance, at least, man was right and the satyr wrong. But if this surprised him, what would he think of the wonders of modern chemistry, of seeing, for example, one fluid frozen and another made to boil by the same means? If we take, for instance, a small tin cup of ether, put it within a watch glass containing water, and place both under the receiver of an airpump, it will be found, on exhausting the receiver, that the water will freeze and the ether boil. The reason is, as the air is expanded, the ether, by its own caloric, and absorbing caloric from the water, is converted into a gas, which escapes in ebullition, while the loss of caloric suffered by the water converts it into ice.

QUERIES.

To the Editor of the Chemist. SIR, You would greatly oblige a constant reader by inserting the following query:-I wish to ascertain if a more expeditious method

TO DETERMINE SPECIFIC GRAVITIES.

Ir the body be a solid, fill a phial with water, and note its exact weight in grains. Take a hundred grains of the substance to be examined and drop it into the water; now weigh the phial again, and the difference between its present and former weight will give the specific gravity of the substance. If the body be a liquid, a bottle or phial, the weight of which is known, and which holds exactly five hundred or a thousand grains of water, is to be filled with the substance and weighed: the weight, deducting the weight of the bottle, will be the specific gravity of the substance. For example, if the bottle contain a thousand grains of water, and be filled with sulphuric acid, it will be found to weigh from 16 hundred to upwards of 18 hundred grains, and the weight will be the specific gravity.*

For an explanation of specific gravity, see Chemist, No. XXIV., Article, Chemistry.

nature,

SO

FRAGRANT LAMPS. MR. EDITOR,-Perhaps you may thank me for the following little account of a method of preserving the air of apartments comparatively pure, and at the same time of dispersing a pleasant fragrance through them. By means of a wire fixed to one side or at the back part of the lamp, according to its c, and bent at right angles, as to be a few inches above the top of the flame, a piece of sponge is to be suspended. This is to be soaked in a mixture of best vinegar and water, and squeezed nearly dry before it is hung up. By this ineans vinegar is constantly dispersed through the apartment, and gives a very fragrant smell. It would probably be very useful in manufactories and close workshops, and is of course as easily applicable to g gas as other lights. It costs very little, for the same piece of sponge has served me a whole winter. It must be occasionally re-immersed in the water and vinegar, and then will be found to give out a great quantity of soot, which otherwise fouls the air of the apartments.

Your obedient servant,
EIN DEUTSCHER.

DISTINCTION OF POSITIVE AND NEGATIVE ELECTRISA CITY nit may by An 12 POSITIVE and negative electricity In may be readily distinguished by I the taste, on, making the electric De current pass by means of a point on to the tongue. The taste of the positive electricity is acid; that of

DESCRIPTIVE HISTORY OF THE STEAM-ENGINE.

(Concluded.)

AFTER Savery's engine became known, a great deal more attention was directed to the subject than before; and the names even of those who were successful in their attempts to improve it, would occupy no inconsiderable space. In Savery's engine, the effect is produced by the condensation of the steam forming a vacuum in a receiver, into which the water is forced by the pressure of the atmosphere; and where the water was required to be elevated to a greater height than from 28 to 30 feet, he bemployed the direct pressure of high pressure and dangerous elasticity; It could only,

however, be applied with safety to raise water about 30 feet. A very short time after the publication of Savery's book, Thomas Newcomen, a blacksmith, and John Cawley, a glazier, both living in the town of Dartmouth, in Devonshire, "made the experiment of introducing steam under a piston moving in a cylinder, and formed a vacuum by condensing the steam by an effusion of cold water on the outside of the steam vessel, and the weight of the atmosphere pressed the piston to the bottom of the cylinder. This was the first form of the atmospheric engine, the simplest and most powerful machine that had hitherto been constructed. In the atmospheric engine the process is totally different from that in

Savery's engine; the steam exerts no direct action upon the water, or on any part of the apparatus, it is merely employed as a means of forming a speedy vacuum under a piston attached to one end of a lever, the rod of a pump piston or plunger being affixed to the other extremity." Of this first atmospheric engine we shall subjoin, with Mr. Stuart's permission, his description:

"In this construction the power of the engine has no reference whatever to the strength or temperature of the steam, but depends upon the superficial dimension of the piston beneath which the vapour is introduced from the boiler. The steam cylinder, T, was now, for the first time, effectually detached from the water-pump.

"The steam generated in a boiler, b, was admittted through the cock, d, and pipe, q, intò a cylinder, a, under the steam piston, s, attached by the rod, r, to the lever or beam, ii, moving on the axis or fulcrum, o. The cylinder, a, was placed in another cylinder, forming a concentric space, zz, round it. This outer cylinder was connected by a pipe, f, to a reservoir, g, containing cold water. Another pipe proceeding from its lower end was inserted into the well or second reservoir of cold water.

"The piston being in the position shown in the Figure, and the cylinder, a, being filled with steam through the pipe, q, the cock, d, is turned, which shuts off the communication between

the cylinder, a, and boiler, b. By opening cock f, cold water is now allowed to flow from the reservoir, g, through the pipe, f, into the outer cylinder, zz; this cools the cylinder, a, containing the steam, which condenses the included vapour, and forms a vacuum under the piston, s. The pressure of the atmosphere meeting with no resistance from the elasticity of the steam, forces the piston to the bottom of the cylinder.

"By this movement, the end of the lever, i, attached by the rod, r, to the piston, is depressed; and the other end of the lever to which the pump-rod is fixel, is raised, and draws up all the water above the plunger in the pump barrel along with it.

Now, if we suppose the cold water which has been in contact with the steam cylinder to have condensed all the vapour, the atmosphere will press on the piston with a force equal to that

which would be produced by placing about 14 lbs. weight on each inch of its surface. If the piston were 62 inches square, this would be about 915 pounds weight, operating to force it downwards; and, if there were no resistance from friction, it follows, that in the same time an equal weight placed at the other end of the lever beam, or a column of water, weighing 915 pounds, would be lifted as high as the steam piston had been depressed in the cylinder.

"When the piston has arrived at the bottom of the cylinder, the cock, d, is turned, which again opens a communication between the boiler, b, and

the steam cylinder, a. In this engine, the steam being only equal to the pressure of the atmosphere, the piston, s, must be raised by other means to the top of its cylinder. This is effected by a counterpoise, m, fixed on k, which is so adjusted as to depress the pump rods, and thus to raise the steam piston into the required position. During this operation the cock, f, is shut, and the cock, e, is opened, and the water heated by the condensation of the steam in the condensing cylindér, z, escapes into the well or tank, o. A very small quantity of water being formed in the steam cylinder, a, by the condensation of the vapour, is allowed to fall through the pipe, P, into the same receptacle. The cylinder being a second time filled with steam, the cock, f, is opened, and cold water flows from the reservoir, g, into z; the steam under the piston is again condensed. The pressure of the atmosphere a second time having the preponderance, the piston is depressed, and the pump rod at the opposite end of the lever beam is elevated, lifting up the column of water in the pump barrel as before. By closing cock f, opening e and d, the counterpoise, m, again acts to raise the piston, s, and the operation may thus be indefinitely repeated.

"The fire-place under the boiler is shown at n, the ash-pit at w; xx are the smoke flues; N is a safety-valve; ca gauge pipe, as in Savery's engine; u a wall or post supporting the axis, v, of the lever beam, ii; tt a pipe connected with the pump barrel, in which the cold water rises to supply the reservoir, g; vl is the mouth of the well or mine which is to be drained; pipe proceeding from g, through which water flows on the top of the piston to keep it air-tight, a contrivance first used by Newcomen."

a