electrics merely relative to the powers of air, and governed by the relative powers of each to the other, as partial conductors and partial electrics?

These questions, and the consideration of all the facts, lead to the general conclusion,-that there is no fluid sui generis producing electrical phænomena-nor any peculiar fluid, nor any fluid whatever concerned in electrical phænomena-and that all this class of phænomena arises from the mechanical decomposition, or temporary separation of the constituent elements of the atmospheric air, or electric medium or fluid interposed between conducting surfaces, within which electrics all the phænomena take place, as well between them and conductors, as between them and other adjacent electrics, and between them and other electrics and conductors.

Electricity is, therefore, an accident of air, or of the atoms of air, just as wind is an accident of air in mass; and it would be as rational to refer a storm to a peculiar fluid, as it is to refer the phænomena called electrical, to a peculiar fluid.

But at the time when the peculiar fluid was first invented, the constituent parts of air had not been discovered, just as the twofold motions of the earth were not suspected when the fall of bodies was superstitiously ascribed to the earth's attraction; or just as the rotation of the earth round the fulcrum of the earth and moon was not suspected when the tides were superstitiously ascribed to the attraction of the moon. But new facts and improved reasoning render it highly proper to get rid of all these properties per se, fluids sui generis, and attractions without mechanical cause! Philosophy must be cleared of them, or the schools of philosophy will soon be as contemptible for their appeals to faith, as any of the temples of any superstition with which ignorant tribes are abused by a selfish priesthood, in any part of the world.

Behold how beautiful and simple electricity rises on the wreck of the superstitions with which it has hitherto been entangled! The excitement, whatever it be, is mechanical, and it produces the mechanical effect of separating the constituent atoms of an affected or electrified plate of air or other electric.

If we excite glass, &c. we produce a preponderance of the acid or oxygen atoms on the proximate surface of air, and the withdrawing of these necessarily occasions an apparent preponderance of alkaline or azotic atoms on the opposed surface which it has hitherto been so difficult to understand.

If we coat the glass surface with a conductor, or congeries of atoms more capable than glass or air of conducting heat or atomic motion, we then unite or connect the points of the electric plate or plate of air.

If we present a similar coated surface in opposition to the first excited plate, we then produce a maximum of effect, i. e. two surfaces which unite all the points of the surfaces of the plate of air, one of which is oxygenated, or positive, and the other azotic, or negative, both exerting considerable force to co-mix in that state of fitness which rendered them atmospheric air *.

If then any light body, or body whose inertia is less than the force with which the atoms seek to reunite, be presented between the surfaces, or to one surface (the other being supposed or understood, and existing in the hand, the operator, or the walls), then the said body will be driven or apparently attracted, and will assist in restoring the equilibrium of the affected electric plate.

If the surfaces be moved so near, that the excitement which separated the atoms is overcome by the aptitude of their forms to reunite, and if any small point project on either surface, carrying the surfaces nearer by the thickness of the said point, then the reunion of the entire surface takes place through that point, and the concentrated force of the simultaneous rush of the oxygenous atoms in one direction, and the nitrogenous atoms in the opposite, produces the action called light; and also mechanical effects on all bodies which contain either oxygen or nitrogen.

The restoration, the double current, the spark (the stream being an optical illusion), and most of the other wonders vanish therefore when examined by a rational mechanical theory.

The great phænomena of nature, which take place when a vast affected plate of the atmosphere is coated by clouds, are easily understood. Some exciting cause, generally the atomic motion of heat, has decomposed the air; but the effects are dissipated in space, till a cloud coats the upper surface, and connects all the points of the affected plate of the atmosphere. Under these circumstances some cloud or point of a cloud, sinking below the general level of the surface, or some projecting point on the earth, narrows the plate in that place, and a concentrated restoration, or partial restoration, takes place at that point, exhibiting lightning, &c. &c. in such imposing grandeur that priestcraft in

**

Thirty-two years ago the writer made his prime conductor of a board covered with tin-foil, and adopting the principle that every conductor is, in fact, but a coating to a plate of air, he arranged similar boards above and below, and thereby decomposed a double plate of air. Galvanism was then unknown; but if he had heard of the Voltaic pile, he would certainly have imitated it in a common electrical circle. He conceives that the ACCELE RATED POWER gained in this way would be far more splendid than in the galvanic circle, because, in electricity, the power is expanded and results from the energy of natural restoration; but in galvanism the exciting power is limited, and not restored, but dissipated.

all

all ages has seized upon it as means of terrifying the ignorant and superstitious.

One might trace, examine, and easily explain all the details of the phænomena on this simple and natural theory; but enough has been said to show that ELECTRICITY is no exception to the mechanical principles of matter and motion-and in regard to the kindred phænomena of GALVANISM, I will content myself with observing, that it is merely ACCELERATED ELECTRICITY, the interposing fluid being palpably decomposed and evolving the electrical powers, each term in the series of plates being a new impulse or power added to the previous one, till the ultimate effect is accelerated, like that of a body falling by the continuous impulses of the earth's motions, or like a nail heated red-hot by accelerations of atomic motion produced by repeated percussions of a hammer.

July 11, 1920.

XXXII. The Bakerian Lecture. On the Composition and Ana lysis of the inflammable gaseous Compounds resulting from the destructive Distillation of Coal and Oil, with some Remarks on their relative heating and illuminating Powers. By WILLIAM THOMAS BRANDE, Esq. Sec. R. S. Prof. Chem. R. I.*

THE experiments detailed in the following pages were origi

nally undertaken with a view of ascertaining the relative fitness of the gases obtained by the decomposition of coal and oil for the purposes of illumination, and of elucidating some apparent anomalies in their economical applications. Merely as such, however, I should not have deemed them of sufficient novelty or importance to form the subject of the Bakerian Lecture; but during the progress of the inquiry, some new views relative to the constitution of these gaseous mixtures suggested themselves, and some properties of terrestrial radiant matter became apparent, which I trust will be thought worthy the attention of this Society.

SECTION I.

On the inflammable gases afforded by the destructive distillation of pit coal and of oil.

The gases used in the following experiments, except where it is otherwise expressly stated, were those employed for the common purposes of illumination; the coal gas being that supplied

* From the Philosophical Transactions for 1820, Part I.

from

from the Company's works in Westminster, and the oil gas furnished by the decomposition of common whale oil, in an apparatus erected for that purpose by Messrs. Taylors and Martineau, at Apothecaries' Hall*. These gases have been submitted to analysis by different chemists of eminence; and we are more especially indebted to Dr. Henry for a series of valuable researches respecting their production and compositiont. It is therefore with considerable diffidence that I venture to propose views relating to them in many respects different from those of my predecessors in this important branch of chemical inquiry.

It is generally admitted, that there are two definite compounds of carbon and hydrogen; the one, usually termed olefiant gas, consisting of one proportional of carbon and one of hydrogen; and the other called light hydrocarburet, composed of one proportional of carbon and two of hydrogen: the former of these gases appears to have been discovered in 1796, by the associater Dutch chemists, Messrs. Bondt, Dieman, Van Troostwick, and Lawerenbourg, and the other first examined by Mr. Dalton§. Assuming hydrogen as 1, the specific gravity of olefiant gas is 13,4; and it contains 1 proportional of carbon =5,7 +1 proportional of hydrogen=1. Light hydrocarburet has generally been considered as consisting of 1 proportional of carbon=5,7+2 proportionals of hydrogen 2, and its specific gravity has been stated as 7,7 compared with hydrogen; or as 57365, assuming atmospheric air as 1.

My first object in the examination of coal gas was to ascertain its specific gravity; and I was surprised to find the first that I examined so low as ,4430. There was some variation in different specimens; and the specific gravity of that prepared in the laboratory of the Royal Institution, and purified in the usual way by condensation in cold vessels, and passing through lime water, was as high as ,4940, which is the heaviest that I have yet met with.

Having been led to consider coal gas as consisting essentially of the two varieties of carburetted hydrogen, I imagined that the specific gravity of the light hydrocarburet must have been estimated too high; I therefore prepared light hydrocarburet from acetate of potash, and having separated its carbonic acid by lime, found its specific gravity,687; the specific gravity of the gas from stagnant water, according to Mr. Dalton, is ,600,

* A description and plate of this apparatus are given in the Quarterly Journal of Sciences, &c. Vol. VIII. p. 120.

† Nicholson's Journal, Vol. XI. p. 65. Philos. Trans. 1808. Manchester Memoirs, Vol. III. New Series. Phil. Mag. Vol. XXXII. p. 277. Journal de Physique, XIV. § New System of Chemical Philosophy. New System of Chemical Philosophy.

Vol. 56, No. 269. Sept. 1820.

C c

and

and that from moistened charcoal when purified is ,480*. It became evident, therefore, that coal gas could not consist principally of the two hydrocarburets; nor could the presence of carbonic oxide be suspected, its specific gravity being ,9834. Hence it occurred to me, that the only mode of explaining these apparent anomalies, was to consider coal gas as a mixture of olefiant and hydrogen gases; and the following experiments were undertaken with a view to determine this point.

1. One hundred volumes of coal gas were detonated by the electric spark over mercury, with 200 of oxygen; the carbonic acid was absorbed by liquid potassa, and 36 volumes of pure oxygen remained in the tube. Whence it appears that 100 volumes of the coal gas under examination required for its perfect combustion 164 parts of oxygen; consequently, as 100 parts of olefiant gas require 300 of oxygen, and 100 of hydrogen 50, for their respective combustion, it might be concluded from the above experiments, supposing no foreign gases present, that the 100 of coal gas consisted of about 55 parts of hydrogen and 48 of olefiant gas; a mixture, of which 100 cubical inches would weigh nearly 15 grains, and which closely corresponds with the specific gravity of the coal gas.

2. One hundred measures of coal gas were introduced into a small bent glas tube containing a little sulphur, and inverted in mercury; a red heat was applied until the inclosed gas underwent no further dilatation; and on examining its volume when cold, it was found to occupy 140 measures. If we consider the increase of bulk as resulting from the decomposition of olefiant gas, this experiment gives the composition of coal gas 60 hydrogen and 40 olefiant by volume.

3. One hundred measures of coal gas were introduced into a mercurial gasometer, connected with a second gasometer by means of a platinum tube, in the manner described by Messrs. Allen and Pepys in their Essay on the Combustion of Carbon*. Some small quartz crystals previously heated red hot were introduced into the platinum tube, which was heated bright red; the gas was then passed through it from one gasometer to the other. for about a quarter of an hour. The apparatus having cooled, the gas was found to have sustained an increase of volume =40 parts; it burned with the pale flame of hydrogen; and when detonated over mercury, required scarcely more than half its volume of oxygen, and afforded a very minute portion of carbonic acid. The interior of the platinum tube was lined with charcoal, the crystals were covered with it, and some had assumed a beautiful brown tint.

Henry's Elements, p. 320.

↑ Phil. Trans. 1807. Phil. Mag. Vol. XXIX. pp. 216, 315.