32 Mr. M. Carey Lea on Endothermic 



equilibrium, and in which, therefore, the chemical energies 

 themselves are already striving to form simpler and more 

 stable compounds out of the constituents of the existing sub- 

 stance. For it cannot be admitted that actual chemical changes 

 can be brought about by a mechayiical impulse " (1. c. p. 350). 



In another chapter he says with equal distinctness : — 



" By mechanical means alone no reaction against the force of 

 chemical energy can be brought about. By a shock or blow 

 the molecular structure of chemical compounds can indeed be 

 so far loosened that free play is given to chemical forces ; 

 but against these forces we cannot by mechanical means separate 

 the atoms nor combine them in a definite way " (p. 594). 



These expressions of a distinguished chemist will suf- 

 ficiently indicate what has been up to the present time the 

 opinion of chemists as to the possibility of transforming 

 mechanical energy into chemical. 



In the first part of this paper I believe I have been able to 

 show in a qualitative way the production of true endothermic 

 reactions by mechanical force. In the present part I hope 

 to show an increased number of such reactions, and in one 

 case to exhibit actual quantitative results, at least so far as 

 to obtain the product of the transformation in weighable 

 quantities. 



In the first part decompositions were described that were 

 brought about by simple pressure. Compounds formed by 

 exothermic reactions, and therefore requiring expenditure of 

 energy to break them up, were decomposed. The investiga- 

 tion might probably have been made to include a still larger 

 range of substances. But it was found that the efficiency of 

 pressure was so enormously increased by the addition of 

 shearing motion, that decompositions requiring a force of 

 hundreds of thousands of pounds with pressure alone could 

 be effected by the mere strength of the hand when shearing- 

 stress was used. More than this, decompositions which 

 enormous pressures failed to effect readily took place under 

 the action of shearing-stress*. 



* It would not have been difficult to obtain much greater pressures 

 than those described in the first part of this paper. This could be effected 

 by means of the differential screw. I had planned for a screw with threads 

 of 40 turns in 10 inches and 39| turns in 10 inches respectively. The 

 mechanical efficiency of such a screw is that of one having 320 turns to 

 the inch, if such a thing were practicable, at the same time that a 

 thoroughly strong construction can be obtained. The massive steel nut 

 to advance §• of an inch would require 40 full turns of this screw. 



This arrangement compares as follows with that previously employed. 

 In it to cause the vise-jaws to approach by 1 inch required that the point 

 of the lever at which the force was applied should pass through a space 



