300 Rev. Dr. Irving — On Dynamic Mefamorphism. 



All that he considers the result of shearing seems to me the direct 

 result of the lateral pressure ; shearing, bending, and fracture being 

 simply concomitant items of expenditure of the energy of the lateral 

 pressure. Shearing, bending, and fracture are simply work done 

 in opposition to the force of cohesion ; the force, that is to say, which 

 tends to maintain the molecules of a solid at fixed distances and in 

 fixed relative positions, to which the undeformed mass owed such 

 rigidity as it possessed ; and this important factor Mr. Fisher seems 

 to have overlooked. In both shearing and bending we must also 

 have some molecular friction, with its thermal effect ; but it is not 

 easy to see how even this applies in the case of fracture, which is 

 simply the work of overcoming cohesion. When Mr. Fisher says 

 " this part of the energy is not convertible, etc.," he seems to me to 

 be using the word ' energy ' where he ought to use the term ' work.' 

 Herein appears to lie the fallacy of the whole argument ; and 

 through this, as through a loop-hole, the idea of chemical action 

 seems to insinuate itself.' 



Turning now to Mr. Barker's letter, the first thing that calls for 

 remark is the " direct correlation of mechanical tvork and chemical 

 energy." This is very nicely put ; so nicely that the unwary reader 

 is easily led off the scent. On this I simply ask for an explanation 

 of the word 'correlation.' What lies hid behind that rather big 

 word is the gist of the whole question we are trying to solve. 

 Sorby certainly suggested something of the sort; but we must have 

 something more solid than suggestions, as a basis upon which to 

 construct sound scientific theory. If Dr. Sorby or any one else will 

 show how we can step by step follow such a transformation in 

 harmony with what some of us knoio from years of thoughtful and 

 fairly extensive study at first-hand of the facts and phenomena 

 which form the groundwork of chemical theory, some real advance 

 will be made. Until this is done, we shall have to regard the cited 

 suggestion as no more than a gigantic guess. It may be useful in 

 pointing the way to further investigation ; but to draw deductions 

 from it, as if it were a well-established induction, is altogether 

 unscientific. 



Mr. Harker refers, however, to experiments of Cailletet, Pfaff, 

 and Spring, as affording practical verification of the suggestion of 

 Dr. Sorby. Unfortunately this rough massing together of experi- 

 mental evidence gives us a result of such a neutral character as 

 we are familiar with in ordinary laboratory-processes of alkalimetry. 

 I know some of Cailletet's splendid work very well, but this has 

 hardly any bearing upon the question before us. If Mr. Harker 

 refers to his experiments on the effect of pressure upon the inter- 

 action of zinc and sulphuric acid, or to those of Pfaff upon the 



' An illustration will perhaps make this clear. "We may expend a definite amount 

 of energy furnished either by the muscles of a horse or the fuel consumed in the fire- 

 place of an engine in drawing a series of loaded trucks along a perfectly horizontal 

 line of rails. Work is done in overcoming the friction of the wheels against their 

 axles and against the rails, and in the displacement of a portion of the atmosphere 

 with the movement of the train ; but would any one contend that energy was stored 

 up in the train ? 



