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. They had found 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 ! siderant le grand nombre que 



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



The resulting figures can, of course, , etoiles tombantes, noufi ue pouvons 



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



proximations : they have been con- j myriades d'asteroides semblables a 



siderably increased by more recent une grele dpaisse se jettent dans 



observations. See A. Berry, ' A tous lea sens sur le soleil ou ils 



Short History of Astronomy, ' p. perdent la force vive de leur mouve- 



397. ! ment " (Mayer's ' Schriften und 



- It does not appear that Mayer I Brief e,' p. 264) ; and M. Faye re- 

 brought his " meteoric " hypothesis j marks that the fact that Mayer's 

 of the generation and maintenance ideas are opposed to Laplace's theory 



of the heat of the sun into connec- 



of the origin of the solar system 



tion with the nebular hypothesis of explains how it came about that 



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- 



his theories were never reported on 

 or explicitly mentioned. Leverrier 

 also seems to have ridiculed the 

 meteoric hypothesis, according to 



