light, will depend purely upon the differences of these particles in respect of one another; it not being possible that any part of them should arise from the comparative magnitude of light, which is equally nothing in respect of them all. And thus it seems, that optics and chemistry will, at last, become a master-key for unlocking the mysteries in the constitution of natural bodies, according to the method recommended by Sir Isaac Newton.
Let A, B, C, be three particles, whose magnitude are 3, 2, and 1, respectively. It is evident, that the mutual influences between A and C, B and C, cannot correspond entirely to the ratio which A and B bear to each other, because C bears a different ratio to A from that which it bears to B; and this difference of ratios must have its share in the effects of A and B upon C: whereas had C been a particle of light, it would have been equally nothing in respect both of A and B; and so the mutual influences between A and C, B and C, would entirely correspond to the difference between A and B, and decypher it. Thus the particles of light, by being infinitely smaller than the biggest component ones of natural bodies, may become a kind of communis norma, whereby to measure their active powers.
All the sciences, knowledge of all kinds, may be reduced to the seven general heads following, when they are understood in the latitude here expressed.
First, Philology, or the knowledge of words, and their significations. It comprehends under it the arts of grammar and criticism. Rhetoric and poetry may be referred to it.
Secondly, Mathematics, or the doctrine of quantity. It may be divided into three branches; viz. arithmetic, which makes use of numbers as the exponents of quantity; geometry, which uses figures for the same purpose; and algebra, which comprehends both these, and whose symbols are accordingly so general, as to represent the symbols of the two foregoing parts.
Thirdly, Logic, or the art of using words, considered as symbols, for making discoveries in all the branches of knowledge. It presupposes philology to a certain degree; and must evidently, in the view here given of it, receive great illustrations from mathematics, which is the art of making discoveries in the single category of quantity, by means of the simplest kinds of symbols.
Fourthly, Natural history, or regular and well-digested accounts of the phænomena of the natural world. It may be distributed into six parts, i.e. into the natural histories of animals, plants, minerals, the earth considered as a terraqueous globe, the atmosphere, and the heavenly bodies.
