332 FRAGMENTS 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 
uid 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 Withdrawn 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 
