to the density of one cubic inch of such air we breathe, if that cubic inch was to be expanded so as to fill a globular space whose centre should be the earth, and whose surface should take inside the whole visible creation. Such a medium could convey no mechanical force from the sun, and therefore the medium of space cannot be ponderable. Simple as the argument is, it is unassailable.

ELECTRIC FLUID THE MEDIUM OF SPACE.

Let us take yet another view. All experiments prove that the phenomenon we call electricity, is owing to a disturbance of the equilibrium or natural condition of a highly elastic fluid. In certain conditions of the atmosphere, this fluid is accumulated in the region of the clouds, and by its tension is enabled to force a passage through opposing obstacles, in order to restore the equilibrium. By experiment it is found that dry dense air opposes the greatest obstacle to its escape. As the air is rarefied, this obstacle diminishes; until in a vacuum the transmission may be considered instantaneous. There ought to be, therefore, a greater escape of electricity from the clouds upwards than downwards; and, if space be void, or only filled with an extremely attenuated matter, the electricity of the earth, considered as an elastic fluid without ponderosity, (and no law of condensation from the law of gravity in harmony with its other attributes, will allow us to consider it otherwise,) would long since have left the earth. The same objection applies in the case of the galvanic and magnetic fluids. If we entertain the idea that electricity is a mere disturbance of natural condition, wherein two fluids are united, and that an excess of one is necessarily attended by deficiency in the other, we depart from the first rule of philosophy, which teaches us to admit no greater number of causes than are sufficient to explain the phenomenon. For we fearlessly assert that not a single fact exists in electrical science, which can be explained better on Dufoy’s theory than on Franklin’s; and the former objections would still apply.

NEWTONIAN GRAVITY.

But what is gravity? According to Newton: “Hæc est qualitas omnium in quibus experimenta instituere licet, et propterea per Reg. 3 de universes affirmanda est.” Vide Prin. Lib. Ter. Cor. 2. Prop. vi.

Now the other primary qualities of matter are unaffected by circumstances. The inertia of a particle of matter is the same at Jupiter as on the earth, so also is its extension; but not so with gravity. It depends on other matter, and on its distance from it; and may be less or greater at different times, and in different places. It is, therefore, not philosophical to say that all matter is necessarily ponderous, inasmuch as it is a virtue not residing in itself alone, but needs the existence of other matter to call it into action. If an atom were isolated in space it would have no weight. If influenced by other matter, there must be some physical medium to convey the influence, or gravity is not in accordance with the laws of force and motion. Which horn of the dilemma shall we take? Let us first admit that there is a principle of gravitation, affecting all planetary or atomic matter, and that there exists a highly elastic medium, pervading all space, conveying to us the light of the most distant stars, and that this medium is not affected by gravity. In this summary way, therefore, we have arrived at the pivot on which this theory turns.

The prominent feature of the theory, therefore, is the necessity it will show for the existence of an all-pervading medium, and that it possesses inertia without ponderosity. That electricity is nothing more than the effects of the condensation and rarefaction of this medium by force. That it also pervades all atomic matter, whose motions necessarily move the medium; and, consequently, that there can be no motion without some degree of electricity. That no change can take place in bodies either by chemical decomposition, by increase or decrease of temperature, by friction or contact, without in some measure exciting electricity or motion of the ether. That galvanism and magnetism are but ethereal currents without condensation, induced by peculiar superficial and internal molecular arrangement of the particles of certain substances. That light and heat are effects of the vibrations of atoms, propagated through this universal medium from body to body. That the atomic motion of heat can be produced by the motion of translation or momentum of bodies in the gross, that is, by friction, by compression, &c.; and can be reconverted into momentum at our pleasure. Hence the latent heat or specific atomic motion of combustibles, originally derived from the sun, is transferred to atoms, which are capable of being inclosed in cylinders, so as to make use of their force of expansion, which is thus converted into momentum available for all the wants of man.

GRAVITY MECHANICAL.

When we come to a full examination of this theory, we shall further reason that this ether so far from being of that quasi spiritual nature which astronomers would have us believe, is a fearfully energetic fluid, possessing considerable inertia and elasticity; that its law of condensation is that of all other fluids, that is, as the compressing force directly; and that its effects are simply a product of matter and motion. We will next endeavor to prove that the gravity of planetary matter could not exist without this ethereal medium, by showing that it is an effect produced by the interference of opposing waves, whereby a body is prevented from radiating into space its own atomic motion, from the side opposite which another body is placed, as much as on the opposite side, and consequently it is propelled by its own motion towards the other body. And this effect following the simple law of inertia and radiation, is directly as the mass, and inversely as the squares of the distances.

GREAT PRINCIPLE OF DYNAMICS.

One great principle to be kept in view in this investigation, is that which teaches that the product of matter, angular velocity, and distance from the centre of motion, must ever be a constant quality in every balanced system. Yet this principle does not seem to be observed in the case of the planets. We will, however, endeavor to show that it is rigidly observed. And we will extend the principle further, and contend that all the phenomena of nature are consequences of the constant tendency of matter to conform to this principle of equilibrium, when suffering temporary derangement from the operation of other laws. That throughout the system of nature, equal spaces possess equal force. That what we call temperature, is nothing more than the motion of equilibrium or atomic momentum of space; or, in other words, that if all space were fluid, and in a state of equilibrium, the product of each atom of equal volume, by its motion would be a constant quality. From this it would seem to follow, that the specific heat of bodies should be inversely as their atomic weights; and this does, no doubt, approximately obtain as was proved by Dulong and Petit, for metallic substances, more recently by Regnault, and has since been extended by Garnier to other substances. But it is to the gaseous state that we must look for confirmation of the principle that equal spaces possess equal power; and in doing so, it will be necessary to bear in mind, that the ether also is affected by temperature.

SPECIFIC HEAT.

It has been contended by some that the medium which conveys the impression of light through transparent, bodies, is necessarily more dense