the Heat excited by Frictioiu 483 



When 30 minutes more had elapsed, or i hour and 

 30 minutes after the machinery had been put in motion, 

 the Heat of the water in the box was 142^ 



At the end of 2 hours, reckoning from the beginning 

 of the experiment, the temperature of the water was 

 found to be raised to 178°. 



At 2 hours 20 minutes it was at 200° ; and at 2 hours 

 30 minutes it actually boiled ! 



It would be difficult to describe the surprise and as- 

 tonishment expressed in the countenances of the by- 

 standers, on seeing so large a quantity of cold water 

 heated, and actually made to boil, without any fire. 



Though there was, in fact, nothing that could justly 

 be considered as surprising in this event, yet I acknowl- 

 edge fairly that it afforded me a degree of childish 

 pleasure, which, were I ambitious of the reputation of a 

 grave philosopher^ I ought most certainly rather to hide 

 than to discover. 



The quantity of Heat excited and accumulated in this 

 experiment was very considerable ; for, not only the wa- 

 ter in the box, but also the box itself (which weighed 

 \!^\ lb.), and the hollow metallic cylinder, and that part 

 of the iron bar which, being situated within the cavity 

 of the box, was immersed in the water, were heated 150 

 degrees of Fahrenheit's scale ; viz. from 60'' (which was 

 the temperature of the water and of the machinery at 

 the beginning of the experiment) to 210°, the Heat of 

 boiling water at Munich. 



The total quantity of Heat generated may be esti- 

 mated with some considerable degree of precision as fol- 

 lows : — 



