PRACTICAL STANDARDS I-OK KLECTKICAL MEASUREMENTS. 



57 



position has been summed up by Principal (Jriffiths in the 'Rapports 

 presentcs au Congres International de Physique,' Paris, 1900, tome i., and 

 in his Lectures on the Thermal Measurement of Energy.' They aro 

 also summarised by Professor Everett in the latest edition of his work, 

 ' C.G.S. Units and Constants. ' 



The following table, taken from Professor Everett's work, gives the 

 results adopted by Principal Griffiths. 



From this it follows that the heat required to raise a gramme of water 

 1° on the hydrogen scale is 4-2 joules when the size of temperature is 

 from 7°-2 C. to 8°-2 C. Thus according to this the 10° C. of Proposition II. 

 should be l°-~ C, and a calorie would be the heat required to raise a 

 gramme of water F of the hydrogen scale from 7°-2 to 8°"2 of that scale. 



Tables of Mechanical Equivalents in Joules. 



1 joule = 10" erg.«!. 

 Eowland, reduced by Day. Hydrogen scale. 



' Cambridge TJniversit}'' Press, 1901. 



