52 Reynolds and Moorby, Eqtiivalent of Heat. 



(3) Terminal corrections to the heat. 



In col. 5 the difference of these corrections is given as 

 6 thermal units. The correction to Ki is therefore 



= — o'OOOo64. 



(4) Loss of heat by conduction along the shaft. 



In col. 6 the difference of temperature between the 

 brake and the adjacent bearing is 1*5^'. The loss per i*^ 

 is 12 thermal units. The correction to Ki is = — 0'000i92. 



(5) Loss of heat by radiation. 



In col. 7 the difference of temperature between brake 

 and air has the value — 1° ; assuming 9 for the constant 

 of radiation the correction to Ki becomes =0"000096. 



The total correction factor required on account of the 

 non-elimination of these casual errors is therefore 



1—0-000192. 

 Applying this factor we get 



K2 = Ki(i —o"000 1 92) = 778-06(1 —0-000192) = 777-91. 



This value Kg can also be obtained by dividing the differ- 

 ence of work in col. 2 by the difference of heat (corrected) 

 in col. 8. 



This value Kg now requires a correction factor made 

 up of a number of quantities which are dealt with below. 



8. Corrections to the mean value of K (y/ygi) given by the 

 experiments. 



I. Length of brake lever. 



This correction has been calculated to be 0*00042. 



II. Salts dissolved in Manchester water. 



These amount to 42-1 milligrammes per Htre. Assum- 

 ing their specific heat =0-2, the correction required is 

 0-00003. 



