18 FORCE, A CAUSE OP MOTION. 



generally tlie views we entertain of the conditions of 

 matter in connection with the imponderable forces and 

 mechanical powers. The conversion, as it has been 

 called, of motion into heat, in the experiments of Connt 

 Rumford and Mr. Joule,* are only evidences that a 



* Couot Rumford's experiment consisted in placing a mass of 

 metal in a box of water at a known temperature, and, by employ- 

 ing a boring apparatus, ascertaining carefully the increase of 

 heat after a given number of revolutions. He thus describes his 

 most satisfactory experiment : 



" Everything being ready, I proceeded to make the experi- 

 ment I had projected, in the following manner. The hollow 

 cylinder having been previously cleaned out, and the inside of 

 its bore wiped with a clean towel till it was quite dry, the square 

 iron bar, with the blunt steel borer fixed to the end of it, was 

 put into its place ; the mouth of the bore of the cylinder being 

 closed at the same time by means of the circular piston through 

 the centre of which the iron bar passed. 



" This being done, the box was put in its place ; and the join- 

 ings of the iron rod, and of the neck of the cylinder with the 

 two ends of the box, having been made water-tight, by means of 

 collars of oiled leather, the box was filled with cold water (viz.. at 

 the temperature of 60) and the machine was put in motion. The 

 result of this beautiful experiment was very striking, and the 

 pleasure it afforded me amply repaid me for all the trouble I had 

 had, in contriving and arranging the complicated machinery used 

 in making it. The cylinder, revolving at the rate of about thirty- 

 two times in a minute, 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 generated, and it was not 

 long before the water which surrounded the cylinder began to be 

 sensibly warm. At the end of one hour, I found, by plunging 

 a thermometer into the water in the box (the quantity of which 

 fluid amounted to 18-77 Ibs. avoirdupois, or 2% wine gallons), 

 that its temperature had been raised no less than 47; being 

 now 107o of Fahrenheit's scale. When thirty minutes more 

 had elapsed, or one hour and thirty minutes after the machinery 

 had been put in motion, the heat of the water in the box was 

 142. At the end of two hours, reckoning from the beginning 

 of the experiment, the temperature of the water was found to be 

 raised to 1 78. At two hours twenty minutes it was at 200 ; 

 and at two hours thirty minutes it actually boiled." Inquiry 

 concerning the Source of the Heat excited by Friction : Philosophi- 

 cal Transactions, vol. Ixxxviii. A.D. 1798. 



