Tables 255-257. 237 



MECHANICAL EQUIVALENT OF HEAT. 



TABLE 266.— Summary. 



Taken from J. S. Ames, L'equivalent mecanique de la chaleur, Rapports presentes au congres 

 international du physique, Paris, 1900. 



Name. 



Joule . . 

 Rowland 



Reynolds-Morby . 

 Griffiths . . . . 



Schuster-Gannon 

 Callendar-Barnes 



Method. 



Mechanical 

 Mechanical 



Mechanical . 



Electrical . . 

 E'^t 

 R 



Electrical Eit. 



Electrical Eit. 



Scale. 



C Latimer-Clark = 1. 4342V at i5°C. 



( International Ohm 



f Latimer-Clark = 1. 4340V. at 15° 

 \ C, Elec. Chem. Equiv. Silver 

 ( =0.001 1 i8g 

 Latimer-Clark = 1.4342V. at 15° C 



Result. 



4-173 

 4.195 

 4.187 

 4.181 

 4.176 

 4.1832 



4.198 

 4.192 

 4.187 



4.1905 

 4.179 



Temp. °C. 



16.5 

 10. 



15- 



20. 



25- 

 Mean- 

 calory. 



IS- 

 20. 



25- 



19.1 



40. 



TABLE 256.— Reduced to Qram-calory at 20° 0. (Nitrogen thermometer). 



Joule 



Rowland . . . 

 Griffiths. . . . 

 Sch uster-Gannon 

 Callendar-Barnes 



4.169 X 10^ ergs 

 4.181 " " 

 4.192 " " 

 4.189 " " 

 4.186 " " 



4.169 X lo'^ ergs. 

 4.181 " " 

 4.184 " " 

 4.181 " " 

 4.178 " " 



* Admitting an error of i part per looo in the electrical scale. 



The mean of the last four then gives 



1 small (20° 0) calory=4.181xiO' ergs. 



I small (15° C) calory = 4.185 X 10^ ergs assuming sp. ht. of water at 2o° = o.9990. 



TABLE 257 .— Conversion Factors for Units of Work. 



* g = g.So m. per sec. per sec. at latitude 45°, sea level, 

 t g:= 32. 2 ft. per sec. per sec. " " " " " 



Smithsonian Tables. 



