128 
The Heat of the Sun. 
! March, 
subject to acquire a little preliminary knowledge. Suppose 
a body to be moving and we stop that body s motion, 
knowUiat we have to exert force to do so. Moieovei, the 
heavier the body the greater force is required, or, with the 
same weight, the faster it goes the more force is required. 
Given the weight and the velocity of motion we can calcu- 
late the work required to be done to bring the body to lest. 
Again, it has been proved that work or energy and heat aie 
mutually convertible, — i.e., that a certain amoun o lea 
can be produced by the expenditure of a certain amount of 
work, and also that a certain amount of work will heat a 
given body to a certain degree. This has been cal ed U . 
Mechanical Equivalent of Heat, and we may state 1 - thus 
—If the work required to raise 1390 lbs. one foot high be 
done upon 1 lb. of water, the temperature of that water will 
be raised T C. Now, as was said above, we can calcula 
the amount of work which must be done in order to stop the 
motion of a moving body, and therefore, if this woik be 
transformed into heat, we can find how muchthe ^™ pe h ‘ 
ature of the body will be increased. Thus we find that the 
heat given out by stopping the motion of a leaden bullet 
moving at the rate of 1300 feet a second would raise its 
temperature about 6oo° C., if all the heat were retained by 
th To U the t imagination it is an easy matter to rise from the 
consideration of the impadt of a rifle bullet to consider the 
impact of worlds. In effedt this is what the Meteoric l heory 
does only Tn ste ad of worlds it considers the collision to occur 
between the Sun and meteors and comets . In our so ai 
svstem there exists a numerous class of small bodies called 
asteroids. These small bodies, like the larger ones, are 
subjedted to the law of gravitation, and are attracted by the 
Sun Ar.v medium which exists in space, however raie it 
may be, would exert a comparatively greater adtion upon 
small bodies than upon large ones, such as the planets. 
Thus, although these latter may not have their motions 
affedted, the former may be rapidly caused to approac 1 t e 
Sun. It is thus supposed that the Sun is constantly su je 
to a cannonade of small bodies upon its surface, but it 
such a rain of these small bodies is constantly falling from 
the outermost limits of our system upon the Sun, it is evi- 
dent that as they approach near him they become condensed. 
We ought therefore to be enabled to see such a ciowd 0 
* It is interesting to note here that the idea of the universal existence of 
the atmosphere is introduced in the Meteoric Theory. 
