304 The Rev. 0. Fisher on Mr. Mallet's 



that these are fully sufficient to refute it. He says, "■ indeed the 

 statement that if under any circumstances and in the rock-masses 

 of nature 'crushing can induce fusion, then the cubes experi- 

 mented upon ought to have been fused in the crushing/ seems 

 as unsupportable as it would be to affirm that no heat is developed 

 by the slow oxidation (eremacausis) into water and carbonic acid 

 of a pound of wood, which when burned develops a well-known 

 amount of heat/-' I may observe that I made no statement 

 about the " rock-masses of nature/'' but simply commented on 

 Mr. Mallet's arguments, such as I understood them to be; for 

 I did not see the bearing of the numerous and elaborate experi- 

 ments, and laborious calculations founded upon them, unless it 

 was held by him that the results as he had left them were held 

 by him to be applicable to the case of nature. I certainly sup- 

 posed that such was the author's meaning ; and it seems that 

 Professor Hilgard came to the same conclusion. I am also at 

 a loss to perceive how the instance of eremacausis bears upon the 

 question. If it represents the cubes crushed in air, and the quick 

 burning represents the rock crushed low down within the crust, 

 then it would support the view that the heat developed in both 

 cases is the same; for the total amount of heat developed by the 

 burning of the wood is the same in either case, though the times 

 taken to develop it differ.' In Mr. Mallet's experiments time 

 does not enter as a factor; for the work is measured by pressure 

 X distance through which it acts, and no deduction is made on 

 account of any escape of heat. 



We will now follow Mr. Mallet into his developments of the 

 original theory, as given in his paper " On the Temperature 

 attainable by Rock-crushing and its Consequences."" 



" If a cube of rock, which in free air is found to crush under 

 a certain pressure, be situated deep within a mass of similar rock 

 and there crushed, it does not admit of dispute that the work 

 necessary to effect crushing must be largely increased." 



This does not appear easily reconcilable with the statement of 

 § 92 of the original memoir. But, admitting it to be the case, 

 and that the pressure required to crush cubes at the depths of 10 

 and 20 statute miles will be as supposed 2*14 and 4"28 times as 

 great as in air, it of course follows that "if we assume the dis- 

 placement of the crushed particles after crushing to be the same 

 as in the case of the cube crushed in air, then the work and the 

 heat due to its transformation will be also 2*14 or 4 # 28 times 

 as great." But it seems impossible that a cube of rock so situated 

 could be reduced to a cake of considerably increased diameter, 

 as were the cubes experimented on ; and therefore if one factor 

 in the expression for the work should be increased, as Mr. 

 Mallet believes, the other must be at the same time greatly 



