480 Correspondence — Itev. Dr. Irving. 



potential energy of position becoming kinetic, without taking aught 

 from the force, with which gravitation continues to act upon the 

 portion of the earth's lithosphere, to whose descent towards the 

 earth's centre of gravity the lateral thrust is due. The clock has 

 merely run down, as it appears to me. Work has been done, and that 

 work is the equivalent of the potential energy. In the infinitesimal 

 amount of molecular change in the iron (where bad material is 

 used), which I had overlooked, and Mr. Fisher recognizes as a case 

 of " dynamo-metamorphism," we have indeed an excellent example 

 (so far as it goes) of metatropy resulting from the action of forces 

 purely mechanical, as I have contended for the last three years ; 

 but as this is quite a different thing from what we understand by 

 chemical change, there is no " storage of chemical energy," which is 

 the C7-UX of the whole business. 



Turning now to Mr. Barker's rather donnish letter (p. 431), in 

 which he persists in regarding the phrases " chemical combination " 

 and " chemical change or action " as convertible terms, 1 can only 

 say that there is nothing to be gained by discussing that point 

 further. The remainder of the paragraph is, I think, answered by 

 anticipation in what 1 have already written. I certainly have main- 

 tained that ever since this globe began to cool down in space through 

 dissipation of its energy by radiation, that cooling has been (and is 

 still) retarded by a considerable exothermic balance of heat, as 

 mineral changes in the lithosphere have upon the whole advanced 

 from less stable to more stable states of combination ; and in doing 

 so 1 take my stand upon the broad teaching of thermal chemistry 

 in its recent development. It is there that Mr. Barker must look 

 for the "proof" that he wants. Perhaps Prof. Eoberts- Austen's 

 recent address to the Chemical Section of the British Association at 

 Cardiff may help him. To his appeal to an imaginary consensus of 

 " physicists " it is, I think, a fair reply that there are physicists and 

 physicists ; and that, although a good deal of what I have written 

 (in the Geological Magazine and elsewhere) may seem to some 

 of them to be written in an " unknown tongue," I am happy to 

 know that there are others to whom it is all perfectly intelligible. 

 The term " intensity of heat," for example, is used to emphasize 

 the inverse variation of absolute temperature in relation to dis- 

 tribution in time and mass (allowance being made for what Sir 

 William Thomson calls "diffusity") for a given quantity of heat, 

 as velocity and mass are related in the momentum of a body in 

 motion. The term must stand on its own merits. 



The importance of the indirect action of pressure in promoting 

 chemical change, by making the existence of superheated water 

 possible (the action of which is exceedingly well illustrated by the 

 recent work of Kroutschoff) is not, I think, lessened by the failure 

 of our two friends to appreciate it. There is surely in this a storage 

 of potential chemical energy. Why do they refuse to use the weapon 

 placed in their hands ? ^ Irving. 



"Wellington College, Berks, 8th September. 



