48 Correspondence — Mr. Alfred Harher. 



carbon is heated in carbonic acid gas, C O is formed with a disap- 

 pearance of heat ; and, when nitrogen and oxygen are sufficiently 

 heated together, an oxide of nitrogen is formed with a disappearance 

 of heat ; and, that in these cases the heat which has disappeared has 

 become chemical energy in the molecules of C or N 0. Whether 

 it be atomic energy or not is not at present known, but as the mole- 

 cule includes the atoms, it is certainly "molecular" as distinguished 

 from ordinary mechanical, or molar energy. Since many chemical 

 changes, which only take place at very high temperatures, appear 

 to be attended with a disappearance of heat, it is at least not im- 

 probable that some of the changes, by which minerals are formed 

 in the interior of the earth, may also be attended with a storage of 

 energy." 



" Perhaps Dr. Irving takes exception to the supposition that 

 mechanical energy may be directly transformed into chemical 

 energy. If so, you may reply that the known effects of pressure 

 upon chemical changes, when those changes are attended by a 

 change of volume, afford support to the supposition. Kecent obser- 

 vations on the influence of surface tension on chemical change by 

 Liebreich, J. J. Thomson, and others, lead in the same direction, 

 so that it cannot be said that the supposition is unreasonable, even in 

 the light of recent advances in physical chemistry." 



Finally I am told that the assertion that " chemical combination 

 must generate heat" is certainly incorrect, and that the examples CO 

 and NO to the contrary are " only two out of an immense number." 



Harlton, Cambridge, 13 Dec. 0. FiSHER. 



DYJSTAMOMETAMORPHISM. 



Sir, — I must apologize to Dr. Irving for having overlooked the 

 observations to which he refers. Unfortunately I had not read the 

 work in question at the time when I wrote my letter. 



As regards the main subject of his letter in your December num- 

 ber, I would offer only a few words. In assuming that the whole 

 of the work done in the compression, deformation, and friction of 

 rock-masses passes into heat, Dr. Irving misses the idea which 

 underlay the whole of my remarks, and was more explicitly stated 

 in Mr. Fisher's article. The direct correlation of mechanical and 

 chemical energy was, I believe, first mooted by Dr. Sorby in 1863 ; 

 but the practical verification of it rests on such experiments as those 

 of Cailletet, Pfaff, and Spring. To take an example : Spring sub- 

 jects a mixture of sulphur and copper filings to a pressure of 5000 

 atmospheres, and finds it converted into crystallised copper sulphide. 

 The operation is conducted slowly, and the temperature of the 

 apparatus kept constant. In other words, so much of the mechanic- 

 ally-developed energy as takes the form of heat is carefully removed; 

 but chemical combination still takes place. It follows that the 

 energy absorbed in this combination comes directly from the me- 

 chanical work done, without the intervention of heat. 



St. John's College, Cambridge. Alfred Hauker. 



