1885.] 
129 
The Heat of the Sun. 
meteors before they fall into the Sun. This is supposed to be 
proved by the existence of the mass of hazy matter which 
ui rounds the Sun, known as the Zodiacal Light. Whether 
01 not this consists of an assemblage of meteors it is, of 
course impossible to say ; but the matter composing it has 
“r ‘he ordinary laws of planetary rotation, 
and thus to behave exactly as meteors would. 
Snn Tf are ^° way l, in which a bod y may fall into the 
Sun . it may fall direaiy upon it, or it may revolve around it 
Tbf‘ fi dU f y . dlmmish u in g orb i ts until it is at last absorbed, 
the hnal velocity which it would have is very different in 
’V” the 1 ! lr f t ’ su PPosing it to fall from an infi- 
te distance, it would have the greatest velocity possible 
mz '> 39 ° miles a second. In the second case, where the 
velocity may be supposed a minimum, it would be equal to 
:^; lesa sec ond. Striking the Sun with its maximum 
velocity the body would generate “ more than 9000 times 
IfppT g o? ei , ated byth . e combustion of an equal ” amount 
ot coal. Stnking with its minimum velocity, it would pro- 
duce 4000 times as much heat. 1 
“ Here, then we have an agency competent to restore his 
lost energy to the Sun, and to maintain a temperature which 
tar transcends all terrestrial combustion. . . . It may be 
contended that this showering down of matter necessitates 
the growth of the Sun : it does so, but the quantity neces- 
saiy to maintain the observed calorific emission for four 
thousand years would defeat the scrutiny of our best instru- 
ments.”— ( Tyndall.) 
Ihe amount of heat generated by the fall of these 
meteors is thus undoubtedly sufficient to produce the temper- 
ature we find, and there also can be no doubt as to the number 
0 tlTese bodies existing in the Solar System. When we 
lemember the large number of meteors which are seen by 
observers, also that the vast majority can only be seen at 
night, and the small bulk which the Earth occupies in space 
we cannot but admit the sufficiency of the cause in regard 
to quantity. Thus during one observation at Boston there 
weie observed, ;n nine hours, no less than 240,000 meteors • 
and thus in a year we may conclude that hundreds, perhaps 
lousands, of millions fall into the Earth’s atmosphere. 
Sir William Thompson, in developing this theory in the 
paper before mentioned, has modified it somewha't. His 
hist idea vyas similar to that of Mayer, that the meteoric 
* matter raining down on the Sun circulated close to him. 
But if there be this matter existing round the Sun, it is 
difficult to account for the fadt that comets are observed to 
