440 Prof. F. Rosetti's Experimental Researches 



constant for a certain time. Then, at a given signal, an as- 

 sistant pushed the flame aside, and another assistant placed 

 the calorimeter-receiver under the ball and immediately raised 

 it, so that the ball dipped into the water of the calorimeter. 

 The work was all done so quickly that there was little fear 

 about the cooling of the ball between the removal of the 

 flame and the immersion in water. 



The calorimeter employed was a double-walled vessel, pro- 

 vided with a thermometer (protected by a brass sheath) and a 

 brass stirrer ; the vessel also had a wooden handle, by means 

 of which it could readily be moved. The thermometer was 

 graduated into fifths of a degree, and had been compared with 

 a standard. The water equivalent of the calorimeter with the 

 thermometer and agitator had been determined by prelimi- 

 nary experiments. Half a litre of distilled water was poured 

 into the vessel. If we call 



Q the weight of the water poured into the vessel, 



q the water equivalent of the vessel with thermometer and 

 stirrer, 



t\ the temperature of the water before the immersion of the 

 ball, 



t 2 the temperature of the water after the immersion of the 

 ball. 



t the temperature of the heated ball, 



p the weight of the ball, 



c the mean specific heat of copper between t x and t 2 , 

 we have (Q + ^)fe-ii)=M^^) 3 



from which the value of t can be calculated. 



The quantity c has been determined by Bede (Wullner, 

 Physik, vol. iii. p. 436, 1872), who found " 

 c=0-0910 + (M)00023(* + * 2 ). 



The experiments from which Bede established this formula 

 did not extend beyond 247°. For want of a better, I had 

 to assume that the same formula might be employed even for 

 much higher values of t. Of the numerous experiments which 

 I made I shall only quote two. 



In the first the surrounding temperature was 11°: — 



Q=498-2, q= 32-5, £=10-58, 

 t 2 = 29-18, p = 123-33; 



by the two preceding formulas we have 



c = 0-1092, *=762°-l. 

 In the second: — 



^ = 11-15, t 2 = 29'W, *=756°-63. 



