XX11 INTRODUCTION. 



a quantity which actually raised the temperature of upward of 

 113 pounds of gun metal at least 70, could have been furnished by 

 so inconsiderable a quantity of metallic dust, and this merely in 

 consequence of a change in the capacity for heat? " 



To measure more precisely the heat produced, he next sur- 

 rounded his cylinder by an oblong wooden box in such a manner 

 that it could turn water-tight in the centre of the box, while the 

 borer was pressed against the bottom. The box was filled with 

 water until the entire cylinder was covered, and the apparatus was 

 set in action. The temperature of the water on commencing was 

 60. He remarks, " The result of this beautiful experiment was 

 very striking, and the pleasure it afforded amply repaid me for all 

 the trouble I had taken in contriving and arranging the complicated 

 machinery used in making it. The cylinder had been in motion 

 but a short time when I perceived, by putting my hand into the 

 water and touching the outside of the cylinder, that heat was gen- 

 erated." 



As the Trork continued the temperature gradually rose ; at two 

 hours and twenty minutes from the beginning of the operation, the 

 water was at 200, and in ten minutes more it actually boiled ! 

 Upon this result Eumford observes, " It would be difficult to de- 

 scribe the surprise and astonishment expressed in the countenances 

 of the bystanders, on seeing so large a quantity of water heated 

 and actually made to boil without any fire. Though there was 

 nothing that could be considered very surprising in this matter, 

 yet I acknowledge fairly that it afforded me a degree of childish 

 pleasure which, were I ambitious of the reputation of a grave phi- 

 losopher, I ought most certainly rather to hide than to discover." 



Eumford estimated the total heat generated as sufficient to raise 

 26.58 pounds of ice-cold water 180, or to its boiling point; and he 

 adds, " from the results of these computations, it appears that the 

 quantity of heat produced equally or in a continuous stream, if I 

 may use the expression, by the friction of the blunt steel borer 

 against the bottom of the hollow metallic cylinder, was greater 



