INTRODUCTION. 



own solar system, as we learn from, an important conversa- 

 tion which he had at Kensington with Conduit (Cosmos, 

 vol. i, p. 120). The uniform image of homogeneous gravi- 

 tating matter conglomerated into celestial bodies has occu- 

 pied the fancy of mankind in various ways, and mythology 

 has even linked the charm of music to the voiceless regions 

 within the realms of space (Cosmos, vol. iv, pp. 431 434). 



Amid the boundless wealth of chemically varying sub- 

 stances, with their numberless manifestations of force amid 

 the plastic and creative energy of the whole of the organic 

 world, and of many inorganic substances amid the meta- 

 morphosis of matter which exhibits an ever-active appear- 

 ance of creation and annihilation, the human mind, ever 

 striving to grasp at order, often yearns for simple laws of 

 motion in the investigation of the teiTestrial sphere. Even 

 Aristotle in his Physics states, that " the fundamental prin- 

 ciples of all nature are change and motion ; he who does not 

 recognise this truth recognises not nature herself" (Phys. 

 Auscult. iii, 1 p. 200 Bekker), and referring to the difference 

 of matter (" a diversity in essence "), he designates motion in 

 respect to its qualitative nature, as a metamorphosis, 

 XXouo<rc9, very different from mere mixture, /*/*?, and a 

 penetration which does not exclude the idea of subsequent 

 separation (De Gener. et Corrupt, i, 1 p. 327). 



The unequal ascent of fluids in capillary tubes the endos- 

 mosis which is so active in all organic cells, and is probably a 

 consequence of capillarity the condensation of different 

 kinds of gases in porous bodies (of oxygen in spongy plati- 

 num, with a pressure which is equal to a force of more than 

 700 atmospheres, and of carbonic acid in boxwood charcoal, 

 when more than one-third is condensed in a liquid state 

 on the walls of the cells) the chemical action of contact- 

 substances which, by their presence occasion or destroy (by 

 catalysis) combinations without themselves taking any part 

 in them all these phenomena teach us that bodies at in- 

 finitely small distances exert an attraction upon one another, 

 which depends upon their specific natures. We cannot 

 conceive such attractions to exist independently of motions, 

 which must be excited by them although inappreciable to 

 our eyes. 



We are still entirely ignorant of the relations which reci- 



