ON THE GENETIC VIEW OF NATURE. 357 



first theoretical and experimental essays, experiments had 

 already been made by Sir John Herschel at the Cape, 

 and independently by Pouillet in France, with the object 

 of measuring the annual expenditure of heat by the 49. 



, . . The heat of 



sun. Ihey had round it to be an enormous quantity, the sun. 

 They represented it popularly by the thickness of a crust 

 of ice on the surface of the earth, which the heat radiated 

 annually by the sun would be able to melt, and they 

 found this to be about 30 metres or 100 feet. Mayer 

 was the first who seems to have put the question 

 definitely : How is this enormous expenditure of heat 

 defrayed, which would, if not in some way compensated, 

 have resulted, even in historical times, in a great lower- 

 ing of the temperature of the sun, and hence also of that 

 on the surface of our globe, such as is contradicted by all 

 historical evidence ? The answer which Mayer gave to 

 this question was based upon an application of his con- 

 ception of the equivalence of heat and the energy of 

 mechanical motion. As the sun, according to the cos- 

 mogonic hypothesis 2 of Laplace, was originally formed by 



1 These measurements were made sideYant le grand nombre que 



in 1837, and very nearly agreed. nous voyons, comme bolides ou 



The resulting figures can, of course, j dtoiles tombantes, nous ne pouvona 



only be considered as rough ap- j pas doubter qu'a tout moment des 



proximations : they have been con- 

 siderably increased by more recent 

 observations. See A. Berry, ' A 

 Short History of Astronomy,' p. 

 397. 



- It does not appear that Mayer 

 brought his " meteoric" hypothesis 

 of the generation and maintenance 

 of the heat of the sun into connec- 

 tion with the nebular hypothesis of 

 Kant and Laplace. In fact, in his 

 first mention of it in his com- 

 munication to the Paris Academy 

 in 1846 he says simply: "En con- 



myriades d'asteroides semblables a 

 une grele e"paisse se jettent dans 

 tous les sens sur le soleil ou ils 

 perdent la force vive de leur mouve- 

 ment" (Mayer's 'Schriften und 

 Brief e,' p. 264) ; and M. Faye re- 

 marks that the fact that Mayer's 

 ideas are opposed to Laplace's theory 

 of the origin of the solar system 

 explains how it came about that 

 his theories were never reported on 

 or explicitly mentioned. Leverrier 

 also seems to have ridiculed the 

 meteoric hypothesis, according to 



