Dr. Woods on the Heat of Chemical Combination. 299 



according to his own calculation. If the ten-thousandth part of 

 any such heat were generated in my experiment, what would 

 have become of the whole apparatus ? 



Or even if we admit that the current consists of electricity 

 which had previously existed in the water, associated with the 

 particles of oxygen and hydrogen as their natural chemical affi- 

 nity, for such Faraday views them, then the two electricities 

 must have passed through the metals, as he admits, and should 

 have destroyed them. Again, if the two electricities did not 

 pass, wby was the minute wire in Wollaston's thimble battery 

 ignited ? and this wire being ignited, why was not the water 

 in my experiment heated to ebullition or total evaporation ? In 

 short, it were endless to express the objections which seem to 

 beset this doctrine of the enormous quantity of electricity asso- 

 ciated with the particles of matter, and which is indispensable 

 to the hypothesis that quantity of electricity at a low intensity 

 is capable of explaining all voltaic phenomena. 



I hope that I have not misconceived Professor Faraday's views. 

 Free to confess that I labour under the disadvantage of not 

 wholly comprehending some of his opinions, I account for it by 

 the fact, which he himself avows, that his doctrine is as yet in- 

 complete. To guard as much as possible against misrepresen- 

 tation, I have quoted his words, and have used them, as far as I 

 could judge, in the sense therein implied, although I am aware 

 that other passages might be selected from the " Researches," to 

 reconcile which some additional helps from the author would be 

 required. 



[To be continued.] 



XLIII. On the Heat of Chemical Combination. 

 By Thomas Woods, M.J). 



To the Editors of the Philosophical Magazine and Journal. 



GENTLEMEN, Parsonstown, Feb. 1852. 



I SHALL be obliged by your allowing the following to appear 

 as an appendix to, or rather as a correction of an error in, 

 my paper on the cause of the Heat of Chemical Combination 

 published in this .dagazine last January. 



In some preliminary remarks on the changes which take place 

 in a beating or cooling body, I endeavoured to show that attrac- 

 tion and repulsion between particles are not necessary to explain 



either expansion or contraction if the law of virtual velocities be 

 extended to those opposite movements which simultaneously 

 OOCUr ', ami that the expansion in one body is the compensation 

 lor the contraction in another; or thai the quantity, so to speak, 



