MODERN SCIENCE. 255 



has ascertained that a MOLECULE of hydrogen MOVES to 

 and fro about 6,200 feet per second, but in such a limited 

 space that it rebounds from other molecules in a second 

 of time 17,000 million times. Further, pursuing the in- 

 vestigations of Loschmidt and Stoney, Clausius and Clerk 

 Maxwell, Thomson was able to determine the size of a 

 molecule : two millions of them in a row would measure one 

 millimetre in length which makes fifty millions in one half- 

 inch the concussions causing waves of coloured light just 

 as a ringing bell causes vibrations and waves of sound. 

 Again, among the problems he has investigated and solved 

 by mathematical or experimental demonstration, Sir W. 

 Thomson may be said to have successfully expounded (1852) 

 the LAW OF DISSIPATION OF ENERGY, which has exercised 

 the ingenuity of several other physicists. According to Sir 

 W. Thomson, "there exists a predominating tendency to 

 the conversion of all other forms of physical energy into 

 heat, and to the uniform diffusion by conduction and radiation 

 of all heat throughout all matter " a fact which would 

 conduce to the uniform cooling, hence extinction of life, 

 of the universe, but which would be counteracted by the 

 general law of conservation of energy determined by Joule, 

 and further, probably, by the Reconcentration of Energy 

 (of Rankine), if the latter be not a mere speculation, for 

 otherwise there would be an end to all physical phenomena. 

 In close connection with this problem Sir W. Thomson has 

 assisted science by removing some of the barriers between 

 its different branches, for " our views of the phenomena of 

 light and heat, of electricity and magnetism, and even of 

 matter and motion, are rapidly merging into a general 

 theory of molecular physics, which is perhaps best ex- 

 pressed by his 'VORTEX RING THEORY,' which was ex- 

 pounded in 1868." According to this theory, "the whole 

 of space is filled up with a fluid ether " as we have already 

 seen in previous notices. Huygens, Encke, Young, Huggins, 

 and others who helped to establish this hypothesis, may be 

 considered as the founders of the present school of Plenum 

 so-called because it holds the doctrine of the existence of 

 one universal and omnipresent ether for (the transmission 



