478 
NEW THEORIES AND FACTS OF HEAT. 
our globe would give rise to a far intenser heat; so that, as 
Ma 3 ^er and Helmholz have calculated, it would not only be 
melted, but a large portion of it would actually be converted 
into vapour. Shooting at a target warms the ball that strikes, 
and the target whieh is struck. Motion is arrested, and an 
equivalent quantity of heat evolved. From this analogy it 
struck Mayer, in 1848, that the sun might have the heat 
whieh he gives out restored by the collision of bodies of 
sufficient size, shot at him with sufficient force ; and the same 
idea has been worked out in this country by Professor 
William Thompson and others.So long as the New¬ 
tonian hypotliesis, that radiant heat consisted in the actual 
emission of particles shot out in all directions from the ra¬ 
diating bod^^, was admitted, the phrase, giving out heat, had 
a distinct and intelligible meaning; but now that this sup¬ 
position is generally abandoned, we cannot consider radiating 
bodies as actual losers of any substance called heat, but 
simply as changing their mode of action as they grow cold. 
While the}^ are hot they can excite heat in other bodies by a 
radiating process under which they themselves grow cooler 
and cooler, unless they experienee a counteraetion of a similar 
or different kind b^" which their heat is restored. Our sun, 
shining day by day, must, in aceordance with this law, grow 
cold in time, unless his own heat receives continual additions 
equal to the amount of his loss. It is assumed—perhaps 
without sufficient warrant—that the sun is hot because he is 
the cause of heat in other bodies; and it is certain that if this 
giant orb follow the law that rules the radiation of caloric, he 
must be constantl}^ losing the capacit}" of warming, and thus 
keeping alive his portion of the universe, unless his heat¬ 
giving power be renewed as fast as it disappears, through 
the taking of some other form. Very slow would be the so- 
called dissipation of his heat; all the future generations of 
man might pass awa}^, our globe might change and change 
again in the arrangement of its materials and the nature of 
its climate, while its fellow-wanderers through the realms of 
space might pass through alterations no less important—there 
might be time, and ample time, for modifications so vast to 
take place; but, however remote the final period might be, 
the sun himself must die,^^ unless his life experiences 
constant renovation, as well as suffers constant deca^,— 
Intellectual Ohserver. 
