DEVELOPMENT OF DAVY'S HYPOTHESIS. 87 



of elastic fluids depends partly on a motion of particles 

 round their axes, has not, I think, hitherto received the 

 attention it deserves. I believe most phenomena may be 

 explained by adapting it to the great electro-chemical dis- 

 covery of Faraday, by which we know that each atomic 

 element is associated with the same absolute quantity of 

 electricity. Let us suppose that these atmospheres of 

 electricity, endowed, to a certain extent, with the ordinary 

 properties of matter, revolve with great velocity round their 

 respective atoms, and that the velocity of rotation deter- 

 mines what we call temperature. In an aeriform fluid we 

 may suppose that the attraction of the atmospheres by their 

 respective atoms, and that of the atoms towards one 

 another, are inappreciable for all pressures to which the 

 law of Boyle and Marotte applies, and that, consequently, 

 the centrifugal force of the revolving atmospheres is the 

 sole cause of the expansion on the removal of pressure. By 

 this mode of reasoning the law of Boyle and Marotte 

 receives an easy explanation without recourse to the im- 

 probable hypotheses of a repulsion, varying in a ratio 

 different from that of the inverse square. The phenomena 

 described in the present paper, as well as most of the facts 

 of thermo-chemistry, agree with this theory ; and in order 

 to apply it to radiation, we have only to admit that the 

 revolving atmospheres of electricity possess, in a greater or 

 less degree, according to circumstances, the power of exert- 

 ing isochronal undulations in the ether which is supposed 

 to pervade space." 



" The principles I have adopted lead to a theory of the 

 steam engine very different from the one generally received, 

 but at the same time much more in accordance with facts. 

 It is the opinion of many philosophers that the mechanical 



