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lows, as in the last experiment, that the 100 measures of coal gas contained 40 of olefiant gas, and 60 of hydrogen.

Mr Brande found chlorine a very useful agent in analyzing the various compounds containing hydrocarburet

. If chlorine and hydrogen are mixed together over water, and exposed to the action of common daylight, but kept out of sunshine, the gases do not act upon one another; and in the course of twenty-four hours, the chlorine will be found to be absorbed by the water, while the hydrogen remains. But if chlorine be mixed with olefiant gas, in the proportion of about three parts of chlorine to one of olefiant, and exposed to the action of daylight, the olefiant, if very pure, will be almost wholly absorbed. From this singular property of chlorine, it may be of great use in the analysis of any mixture of hydrogen hydrocarburet, carbonic oxide, and carbonic acid: for the carbonic acid may be absorbed by a solution of potassa. The remaining mixture being then united with thrice or four times its volume of pure chlorine, and exposed over water to daylight, the carburetted hydrogen, and any overplus of chlorine, will be absorbed : The remaining gas, consisting of hydrogen and carbonic oxide, may be mixed with oxygen, and detonated by the electric spark over mercury. The proportion of oxygen destroyed in the combustion being doubled, will give the hydrogen which was contained in the mixture; and the carbonic acid formed, will exactly measure the quantity of the carbonic oxide. The whole of this mode of analysis depen«ls upon keeping the gas from the action of the solar rays, as it is only the absence of this agency that prevents a combination from taking place between the chlorine and the gases

the mixture. We may mention here, by the way, a very curious effect produced by the action of electric light upon a mixture of chlorine and hydrogen. A tube containing the mixed gases was placed in a darkened room, within an inch of the charcoal points attached to the positive and negative wires of a very powerful Voltaic battery, highly charged. Upon making the circuit complete, the fumes of muriatic vapour were instantly produced; and in consequence of the production of muriatic acid, the water rose in the tube, and very soon the whole of the mixture was absorbed : the gases, too, exploded the moment they were affected by the electric light. These phenomena are similar to those observed in the combination which is produced between chlorine and hydrogen by the action of solar rays. And as the same effects have never yet been produced by the application of any other artificial light, it may fairly be concluded, that this singular agency of light in promoting chemical combination,

that compose

is peculiar to solar and electric rays. Mr Brande was induced to make this experiment, from having failed to produce the slightest effect upon the gases above mentioned, by any flame that could be engendered from the combustion of olefiant gasalthough the light of an argand burner, which he concentrated by means of a lens, produced a heat which raised the mercury in a thermometer placed in the focus, 4°.5 in five minutes. To return to our subject. -

Most of the experiments we have detailed were performed upon the gas procured from the decomposition of whale oil. This

gas is much heavier than that obtained by the distillation of coal. Its specific gravity is .7690; and 100 cubical inches weigh upwards of 23 grains. Now, 100 cubical inches of ole. fiant gas weigh 30.15 grains, and 100 of hydrogen 2.25 grains. Hence, if oil gas consist of these gases only, they will be nearly in the proportion of three volumes of olefiant to one of hydrogen. From these experiments Mr Brande concludes, that olefiant gas is the only definite compound of carbon and hydrogen; and that the various inflammable compounds produced by distillation from coal, oil, &c. consist essentially of a mixture of olefiant and hydrogen gases. We admit that this has so far been established ;-although we might object to the tentative methods which Mr Brande has employed to confirm his conjectures, (pp. 18, 19, 20). A straight forward process would certainly have been preferable; and we are at a loss to understand how he should have omitted to state the result of a method which cannot possibly have escaped him, and which might, more than any other, have strengthened his hypothesis. We allude to the direct analysis of coal or oil gas, by subjecting them to the action of chlorine. By means of this, the olefiant gas being absorbed, the remaining part of the mixture might have been accurately ascertained, both as to quality and quantity: If discovered to be pure hydrogen, the inquiry is at once put at rest; and if mixed with any foreign gases, the presence of such might easily have been detected, either by detonation with oxygen, or by other methods. At all events, it would have been satisfactory to know what such an experiment produced. We are far from explaining Mr Brande's silence on this subject, by supposing that the trial did not prove satisfactory to his hypothesis ; and yet it is difficult to conceive how it should not have been made.

We must also take leave to observe, that in some parts of his inquiry, Mr Brande's train of reasoning is a little fallacious. It is very like what mathematicians call, arguing in a circle. For example; he conjectures, from the specific gravity of oil gas, that it is composed of one volume of hydrogen and three of ole.

fiant. He then makes a mixture in this proportion, and exposes it to the action of heat till the olefiant gas is decomposed-and he finds, of course, that it has increased by the quantity of olefiant gas in the original mixture-which only proves, that the olefiant gas has changed, by decomposition, into double the quantity of hydrogen ;-which he knew beforehand must be the case,-and that the remainder is the hydrogen which he himself put into the mixture, and the quantity of which he might, therefore, have guessed without this process.

He goes on to expose the mixture with chlorine to the action of light-and finds, after the chlorine and olefiant gas have been absorbed, that the original quantity of hydrogen remains in the jar-thus demonstrating that there are six of the one and half a dozen of the other, It surely would have sufficed, if he had told us that, upon submitting chlorine and oil gas to the action of daylight, after the chlorine and olefiant gases were absorbed, the remainder proved to be one-third of the original quantity of the oil gas

of

pure hydrogen-or of hydrogen niixed with other gases, as the case might be.

The latter part of Mr Brande's paper relates to the illuminating and heating powers of the olefiant, the coal, and the oil gases. As some of his results may prove useful in a practical point of view, we shall shortly detail them. The first point is to ascertain the quantity of gas consumed in a given time. For this purpose, a gasometer, with regulating weights which hang over pullies on each side, was used. It contained about 5000 cubical inches of gas, and had jets of different dimensions attached to it, which were furnished in the usual way with stopcocks. The pressure was measured by the difference in the level of the water within and without the reservoir, to which a graduated scale was attached. The gasometer being first filled with olefiant gas, the stopcock of a jet having a single perforation of both of an inch diameter was turned, and the stream which issued from it inflamed ;-the pressure was equal to a half-inch column of water. The light was so regulated as to be equal to that of one wax candle, the intensity being ascertained by a comparison of shadows. In these circumstances, the consumption of gas was found to be 640 cubical ir.ches in an hour;-with oil gas, under the same circumstances, the consumption was 800 cubicat inches in an hour. We are not informed how much coal gas was consumed by a single burner. The next burner employed was on the argand construction, being a circular plate, containing twelve holes, each a'th of an inch in dianieter. “The pressure was the same; and the flame regulated to burn with its full intensity, without producing smoke; and yet

the consumpajon, instead of being twelve times as great as in the case where

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one jet was used, was only 2600 cubical inches in the hour the light being found equal to that of ten wax candles. We can easily comprehend that the light should be as much as this -because the quantity increases in proportion to the elevation of temperature. With an argand burner which gave the light of eight wax candles, the consumption of oil gas was formed to be 3900 cubical inches in the hour. In the burner for coal the apertures require to be larger. Those used by Mr Brande were sath of an inch in diameter: the light was found equal to five wax candles, and the consumption was 6560 cubica! inches in an hour.

It appears from the above data,' says Mr B., that to pro• duce the light of ten wax candles for one hour, there will be • required 2600 cubical inches of olefiant gas, 4875 of oil, and • 13120 of coal gas.

Now, we profess onrselves totally wable to comprehend this arithmetic. We take the data for the ole fiant and oil gases to be, that a burner giving a light coal to one wax candle consumes 640, and a burner giring a lighter qual to ten candles, consumes 2600 cubical inches of olefiant gas, in an hour; that is, to increase the light terfold, the maltiplier must be 4.0625. Now, with the same orifice and pressure, the consumption of oil gas in an hour is 800 cubical inches, to produce a light equal to one wax candle; therefore, it must be 3250 to produce a light ten times as great. Perhaps it may lze, that the single burner did not produce a light equal to one wix candle when oil gas was used, although the quantity of gas consumed was greater,-from the intensity of the light licing. less than in the olefiant gas: but if this be the case, Mr Brande should have so stated it, -as that is the only datum from which we can deduce the consumption when the greater light is produced. In the case of the coal gas, it is certainly erroneous to say, because the consumption in a light equal to fire wax candles is 6560) cubical inches, that therefore double this consumption will be necessary to produce a light equal to ten candles. As well might we contend, that the consumption for a light of one candle being 640, therefore it requires 610 x 10 = 6400 cubical inches, to give a light of ten candles with the olefiant gas, or 8000 cubical inches of oil gas to produce the same light. It may be, that Mr Brande has found by actual experiment,-by a proper adjustment of burners-by an ade quate regulation of stopcocks-by a careful comparison of shadows,-ihat the numbers he has stated are the correct quantities consumed by these different gases in order to produce the same light;-and if so, we have nothing to say ;-but, from the data before us, he has no right to draw these conclusions as matter of calculation.

One thing, however, may be safely gathered from this paper, that olefiant gas is by far the best for purposes of illumination; but unfortunately it is too expensive to be of much practical use. Oil gas is decidedly better than coal, although we apprehend, if our calculations are right, that it is not so superior to it as Mr Brande would make it

appear.

He
says,

that a gasometer containing 1000 cubical feet of oil gas, is adequate to furnish the same quantity of light as one containing 3000 of coal gas.

To ascertain the heating powers of these gases, Mr Brande boiled water over a burner of each, and found, that to raise a quart of water from 50° to 212°, it required 870 cubical inches of olefiant gas-1300 of oil, and 2190 of coal. Hence it is evident, that the air of a room equally lighted by oil and coal gas, will be much less heated by the former than by the latter; a very material considetation, when this species of illumination is introduced into houses. In conclusion, we must call the reader's attention to the

very curious analogy established in Mr Brande's experiments with the battery, between the operation of the solar and electric light; and we strongly recommend the subject also to the author, exhorting him to pursue this inquiry. In a subject where so little is known as that of Electricity, every new view that can be opened is a matter of high interest and importance; and no fact should be disregarded, which may give farther insight into a field still so imperfectly explored.

Art. X. Lectures on the Dramatic Literature of the Age of

Elizabeth. Delivered at the Surrey Instilution. By WILLIAM HAZLITT. London. Stodart. 1820.

IF
F Mr Hazlitt has not generally met with impartial justice

from his contemporaries, we must say that he has himself partly to blame. Some of the attacks of which he has been the object, have no doubt been purely brutal and malignant; but others have, in a great measure, arisen from feelings of which he has himself set the example. His seeming carelessness of that public opinion which he would influence—his love of startling paradoxes and his intrusion of political virulence, at seasons when the mind is prepared only for the delicate investigations of taste, have naturally provoked a good deal of asperity, and prevented the due appreciation of his powers.

We shall strive, however, to divest ourselves of all prepossessions, and calmly to estimate those talents and feelings which he has here brought to

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