352 
REPORT—1854. 
Origin of the Solar Heat. Professor W. Thomsons Theory. 
Some very important speculations have been brought forward on the source, 
and thus bear on the nature, of the solar heat, by Professor Thomson* in 
immediate connexion with the theory of Mr. Joule, and on the principle that 
the energy of the heat thus emitted must be accompanied by an equivalent 
expenditure of mechanical force. On this principle he institutes numerical 
calculations; the main results of which, together with a brief exposition of 
the principles, may be given as follows:— 
The kind of force acting, or the source of solar heat, the author conceives 
may be expressed by several hypotheses, each of which he examines:— 
I. The supposition of the sun being simply a body intensely heated an 
losing its heat by radiation or simple cooling. , 
This he considers quite untenable, as well on theoretical grounds advanc 
in some other papers, as oti the simple consideration that if this were t™ 1 ' 
the sun would be extinguished in a very short time. 
II. The hypothesis of chemical action or combustion of any kind. 
Supposing one of the combining bodies to be supplied trora any a o 
sphere, the products of combustion would be so enormous astochoe 
lire, if gaseous, by preventing the access of the air in question, or, i so' 
or liquid, by preventing the supply of fuel; and according to the mecnam 
theory before mentioned, a numerical calculation shows that the who e m 
of the sun could scarcely last 8000 years, without being allconsume, 
generating, by its own burning, the heat which is actually emitted, ne <• 
if the sun is a fire, the fuel must be supplied from external space. u ^ 
mass of coal or iron or potassium could not reach the sun from eX 
space without generating thousands of times as much heat from its ® 0 ' ' 
as it could possibly do by its combustion. Combustion is probably, ■ 
fore, insignificant, if it exists at all, as a source of solar heat. . 
III. The hypothesis of meteors Calling into the sun and expending 
mechanically, has been started by Mr. Waterstonf, who supposes such 
to be attracted and fall directly into the sun from remote extfa-pw 11 . 
regions. tt ti- 
The supply of meteoric matter necessary according to this theory', “ ■ 
mated to amount to such a mass as would cover the sun's surface to a F 
of 30 feet in one year. ,, jyj 
I he author, however, considers it probable that meteors aC * aa ^ 
into the sun, not directly from distant spaces, but by the actioa °j. a . r . 
ing medium surrounding the sun, which contracts the orbits in which ) 
arc revolving round lmn. He conceives that these meteors must be mov d 
within the limits of the earths orbit, or we should be continually sr 
by them; and that they arc probably the matter of the zodiacal light- ^ 
It is however quite conceivable that that cloud of small planetary 
may once have extended beyond the limits of the earth’s orbit, and ® 
,n m * lote periods the earth may have been exposed to such falls ot tn 
as to have materially raised its temperature; and hence a possible source 
those high temperatures which once existed. , 
But to return to the effects of the resisting medium: owing to its retem» 
turn, the approach of these bodies to the sun is gradual, and on tins hyp* 
thesis a calculation similar to the former would give the result that 
sun must be covered to a depth of GO feet in a year, or a mile in about eig . 
P» rt '■ °" 
t British Association, Hull Meeting, 1853 . 
