VOL. LXXXVIII.] PHILOSOPHICAL TRANSACTIONS. 283 



and 30 minutes after the machinery had been put in motion, the heat of the water 

 in the box was 1 42°. 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 surprize and astonishment 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 surprizing in this event, yet I acknow- 

 ledge fairly that it afforded me a degree of childish pleasure, which, were I ambi- 

 tious 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 expe- 

 riment was very considerable; for, not only the water in the box, but also the box 

 itself, which weighed 15^ 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° of Fahrenheit's scale; viz. from 6o°, which was the 

 temperature of the water, and of the machinery, at the beginning of the experi- 

 ment, to 210°, the heat of boiling water at Munich. The total quantity of heat 

 generated may be estimated with some considerable degree of precision, as follows: 



Of the heat excited there appears to have been actually Q ?l nt }? of . ice " cold water which, 



ri J with the given quantity of heat, 



accumulated, rai S ht have been heated iso dc- 



9 grees, or made to boil. 



In avoirdupois weight. 



In the water contained in the wooden box, 18| lb. avoirdupois, heated 150°, namely, 

 from 60° to 210° F la.2 lb. 



In 113.13 lb. of gun-metal, the hollow cylinder, heated 150° j and, as the capacity 

 for heat of this metal is to that of water as 0.1100 to 1.0000, this quantity of heat would 

 have heated 12g lb. of water the same number of degrees 10.37 



In 36.75 cubic inches of iron, being that part of the iron bar to which the borer was 

 fixed which entered the box, heated 150° j which may be reckoned equal in capacity 

 for heat to 1.21 lb. of water 1,01 



n. b. No estimate is here made of the heat accumulated in the wooden box, nor of 

 that dispersed during the experiment. 



Total quantity of ice-cold water which, with the heat actually generated by friction, 



and accumulated in 2 h 30 m , might have been heated 180°, or made to boil 26.58 



From the knowledge of the quantity of heat actually produced in the foregoing 

 experiment, and of the time in which it was generated, we are enabled to ascer- 

 tain the velocity of its production, and to determine how large a fire must have 

 been, or how much fuel must have been consumed, in order that, in burning 

 equably, it should have produced by combustion the same quantity of heat in the same 

 time. In one of Dr. Crawford's experiments, (See his Treatise on Heat, p.321), 

 37 lb. 7 oz. troy, = 181920 gr., of water, were heated 2-rV degrees of Fahren- 

 heit's thermometer, with the heat generated in the combustion of 26 grs. of wax. 

 This gives 382032 grs. of water heated 1° with 26 grs. of wax; or 1 46934-* grs. 

 of water heated 1°, or '-ff-g- 3 =8 1.631 grs. heated 180°, with the heat gene- 

 rated in the combustion of 1 gr. of wax. The quantity of ice-cold water which 



002 



