332 FRA GMENTS OF SCIENCE. 



through all its applications. Whether the meteoric theory 

 be a matter of fact or not, with him abides the honor of 

 proving to demonstration that the light 'and heat of suns 

 md stars may be originated and maintained by the colli- 

 sions of cold planetary matter. 



It is the man who with the scantiest data could 

 accomplish all this in six short years, and in the hours 

 snatched from the duties of an arduous profession, that 

 the Royal Society, in 1871, crowned with its highest 

 honor. 



Comparing this brief history with that of the Copley 

 Medalist of 1870, the differentiating influence of " environ- 

 ment," on two minds of similar natural cast and endow- 

 ment, comes out in an instructive manner. Withdrawn 

 from mechanical appliances, Mayer fell back upon reflec- 

 tion, selecting with marvelous sagacity, from existing 

 physical data,^the single result on which could be founded 

 a calculation of the mechanical equivalent of heat. In the 

 midst of mechanical appliances, Joule resorted to experi- 

 ment, and laid the broad and firm foundation which has 

 secured for the mechanical theory the acceptance it now 

 enjoys. A great portion of Joule's time was occupied in 

 actual manipulation; freed from this, Mayer had time to 

 follow the theory into its most abstruse and impressive 

 applications. With their places reversed, however, Joule 

 might have become Mayer, and Mayer might have become 

 Joule. 



It does not lie within the scope of these brief articles to 

 enter upon the developments of the Dynamical Theory 

 accomplished since Joule and Mayer executed their 

 memorable labors. 



CHAPTER XXI. 



DEATH BY LIGHTNING. 



PEOPLE in general imagine, when they think at all 

 about the matter, that an impression upon the nerves a 

 blow, for example, or the prick of a pin is felt at the 

 moment it is inflicted. But this is not the case. The 

 seat of sensation being the brain, to it the intelligence of 

 any impression made upon the nerves has to be transmitted 



