THE SOUECE OF HEAT IN THE SUN. 
15'5 
velocity in its fall^ and that if at any point its motion be inter- 
rupted^ that motion will be converted into heat. The black- 
smith's hammer falls upon a bar of iron, and both are heated 
by the blow ; he lifts the hammer and it falls again, when 
double the heat is the result ; he gives a rapid succession of 
such blows, and exactly in accordance with their force is the 
intensity of heat developed, until the iron glows with red — 
this is visible heat. 
Sir Isaac Newton saw the necessity of restoring to the Sun 
the heat and light emitted, and he supposed that comets might 
be the agents employed to gather up force in space, and by 
constantly falling into the Sun, restore that force to it. For 
cometary masses, the modern philosophers — following Mr. 
M^aterston — have substituted meteorites, which are supposed 
to fall — as it were to rain — down upon the Sun. Every one 
of these reaches the Sun with a store of force, represented 
by its motion, and that motion being stopped, heat is the 
result. It has been supposed that the nebulous light of vast 
dimensions which surrounds the Sun, and to which we have 
given the name of the zodiacal light, may indicate the 
crowd of massive asteroids — the rain of fire-balls wdiich is for 
ever restoring the wasting energy of the solar centre. Mayer 
finds — • 
that a mass which after moving in central motion arrives at the Sun’s surface 
has the same velocity as it would possess had it fallen perpendicularly into 
the Sun, from a distance from the centre of the Sun equal to the major axis 
of its orbit ; whence it is apparent that a meteorite, arriving at the Sun, 
moves at least as quickly as a weight which falls freely towards the Sun from 
a distance as great as the solar radius or 441,600 miles. . . . The velocity 
therefore of an asteroid, when it strikes the Sun, measures from 445,750 to 
630,400 metres in a second ; the calorific effects of re-percussion are conse- 
quently equal to from 27^ to 55 millions of degrees of heat (Centigrade) . . . 
An asteroid, therefore, by its fall into the Sun develops from 4,600 times to 
.9,200 times as much heat as ivould he generated hy the combustion of an equal 
mass of coal. 
Calculations have been made to sbow tbe value of known 
masses of matter as restorers of solar energy. It has been 
demonstrated that if our Moon fell into the Sun it would cover 
the Sun^s expenditure of force for more than one and less than 
two years, and the mass of the Earth would support the solar 
energy — that is, it would by its fall into and incorporation 
with the Sun, generate heat sufficient to last the Sun from 60 
to 120 years. 
The meteorites — asteroids — of our system are countless, and 
quite sufficient to meet all the exigencies of the case. It may 
be argued that man has no evidence of any increase in the 
mass of the Sun which it may appear should arise from this 
