Affinity agrees with sensible attraction iti every determinable point :like sensible attraction, it increases with the mass, and diminishes as the distance augments ; consequently, it is just to conclude, that attraction, whether it be sensible or in sensible, is, in all cases, the same kind of force, and regulated precisely by the same general laws.
The threes of affinity, though the same in kind, and possessing the same rate of variation with regard to distances, and also in respect to the mass, are vastly more numerous than those of sensible at traction; for, instead of three, they amount to as many as there are heterogeneous bodies. But even when the distance and the mass are the same, as far as can be judged, the affinity of two bodies for the third is not the same. Thus barytes has a stronger affinity for sulphuric acid than potash has ; for, on equal portions of them being mixed with a small quantity of the acid, the barytes seizes a much larger proportion of the acid than the potash does. The difference of intensity ex tends to all substances, for there are scarcely any two bodies, whose particles have precisely the same affinity for a third, and scarcely any two bodies, whose component parts adhere together with exactly the same force.
Because these affinities do not vary in common circumstances, like magnetism and electricity, but are always the same when other circumstances are equal, it has been argued that they do not, like them, depend on peculiar fluids, the quantity of which may vary ; but that they are permanent forces, inherent in every part of the attracting bodies.
But after the extraordinary discoveries that have been lately made of the power ful effects which electricity, as excited by the galvanic apparatus, has in chemical attractions, and when the great force of the affinity of the bases of potash and of soda to oxygen have been overcome by it, we must hesitate at least in continuing the above opinion, if we do not totally reject it, to adopt its reverse, and consi der electric fire, in future, as the great agent of elective affinities. There is no reason why electric fire may not be sub ject to the same laws of attraction as other substances, and why it may not remain united to bodies in a latent or inactive state, as well as calorie ; we have already shewn, that the mass of any substance has a powerful effect on its degree of affinity ; many of the effects of electric fire on affinity might be explained by this increased power of it, when acting in a mass, or, at farthest, by supposing that its power increased with its mass in a greater ratio than that of other substances.
It has been judiciously remarked, by a respectable chemical writer, that the va riation of intensity, which forms so re markable a distinction between affinity and gravitation, may be only apparent, and not real, and may only arise from the much nearer approach which the parts of one substance may be capable of, to those of a second, than to those of a third; and that thus it may be that barytes at tracts sulphuric acid with greater inten sity than potash, because the particles of barytes, when they act upon the acid, are at a smaller distance from it than the particles of the potash; to which we shall add, that it is possible that the degree of insensible distance to which the parts of substances can approach, depends on the quantity of latent electric fire com bined with them, or in other words, on the degree of their relative attractions to electric fire.
This conjecture of the agency of elec tric fire, in elective attractions, has, at least, the advantage of the atomic theory, which has been advanced to account for the same phenomena, that it relates to matters which we know really exist, and which are not beyond the bounds of hope, indeterminable by experiment. With all due deference to the respectable characters who have used the atomic the ory as an universal explainer, we beg leave to remind its admirers, that it is to tally inconsistent with the laws of sound philosophy, to assume a fact as the basis of an argument, which itself has never had the shadow of proof to support it, and which in its nature is incapable of ex periment. It is idle, in the present re spectable state of science, to talk any more of atoms : as well may we again re vive the dreams of the ancients about the materia subtilis, or those of Des Cartes, relative to vortices, as to reason of the shape, form, nature, and properties of atoms, which, from their very definition, are merely visionary, and which, the mo ment we conceive them as having shape, lose their essential quality of indivisibili ty ; if the existence of atoms cannot be disproved, that is no argument in favour of their existence in the way usually sup posed ; and the atomic theory has only this property, in common with every other which lies beyond the reach of our senses, Judicial astrology, magic, and many other chimeras, cannot be disproved ; but, at least, since the great law of truth has been adopted for philosophy, that no argument was to be admitted in it that was not demonstrable by experiment, or by proof equally satisfactory, mankind has ceased to be led astray by them.