REPORT OF MEETINGS FOR 1901 47 



the high temperature generated within the outer portions of 

 the Earth's crust by dynamic causes still in progress, and 

 operating in the presence of water (usually sea water), which 

 contains various dissolved substances in solution, amongst 

 which the alkalies are the most important. 



As regards the possibility of the generation of heat by 

 dynamic causes, we have but to consider any one of many 

 illustrations, all of which serve to show how this arises. 

 Some of us may remember how schoolboys, wearied with 

 lessons, used to rub brass buttons on the school desks until 

 the friction made the metal hot enough to be uncomfortable 

 to the face or hand of the boy next to him. The operator 

 put a certain amount of energy into the work, which energy 

 was transformed into heat. Again, many persons may have 

 seen a blacksmith, by hammering a piece of annealed iron, 

 raise it to a temperature sufficiently high to ignite the smithy 

 fire. A still more familiar illustration of the transmutation 

 of the energy of motion into the energy of heat is afforded 

 by the application of the brake to the wheels of a railway 

 carriage, when the guard desires to slacken down the speed 

 of the train. In all of these illustrations the heat evolved 

 bears a direct and well-known proportion to the amount of 

 energy employed. It matters not the least whether the motion 

 is rapid or slow ; for just as high a temperature can be evolved 

 by the slow movement of a mountain mass under the influence 

 of a powerful terrestrial thrust, requiring, perhaps, thousands 

 of years to shift the mass a foot, as can be got out of a mass 

 of any smaller dimensions moved at a quicker rate. The 

 principle in both cases is exactly the same ; whether it is 

 a case of a little girl warming a knitting needle by rubbing 

 it on her sleeve, or of two errant stellar bodies colliding, or 

 of the slow upheaval of a great continental mass under the 

 prolonged influence of lateral thrusts ; in each case heat pro- 

 portionate to the energy expended is rendered manifest in some 

 way or other. It is thus, many people now think, that the heat 

 which is the prime cause of volcanic action is generated. 



The temperature requisite for the fusion of rock material in 

 the absence of water is very high, and need not be considered 

 here, because some water is sure to be present. In the 

 presence of pure water the temperature requisite for li<3^ue- 



