at the total solar Eclipse in 1882 371 



If the experiments were to be repeated, I do not know in 

 what particular the conditions of weather, as they were on 

 the forenoon of the i8th, could be made better. Yet if we 

 admit that they might be improved in the proportion that 

 the conditions between 10 and 11 a.m. on the i8th are better 

 than those obtained between the same hours on the i6th, 

 when they were the most unfavourable, the rate would have 

 to be increased in the proportion 57*6 : 807 and it would 

 become 1*5 x 1*4 = 2*1 c.c. per minute. This correction is 

 certainly too great when considered as an allowance for faulty 

 weather, and even if held to cover all instrumental deficiencies, 

 such as imperfect equatorial adjustment and others, I believe 

 it will be still much in excess of the truth ; moreover, I am 



convinced that if the calorimeter furnished steam at this rate 

 it would be in such conditions that it would be impossible to 

 stand by it and attend to it on account of the excessive heat. 



Having thus indicated the maximum correction which can 

 be applicable to our observations we return to the considera- 

 tion of the observations themselves, where we are on the sure 

 ground of experiment. 



In the circumstances we may, without sensible error, take 

 the cubic centimetre of water to weigh one gramme. In 

 specifying quantities of heat we do so in gramme-degrees 

 (Celsius) (gr. C), or kilogramme-degrees (kg. C), as the case 

 may be. Similarly, quantities of work are expressed in kilo- 

 gramme-metres (kgm.). We take the latent heat of one 

 gramme of steam as 535 gr.C, and the specific heat of 



242 



