182 
THE GEOLOGIST. 
for the first 100, and so on until above three miles and a half it takes a 
thousand feet to lose the required degree of heat, — so geologists, in- 
stead of getting even a regular correspondence of 1° Fahr. h)ss tor 
every 63 teet of depth, find a gradual divergence in the ratio of ver- 
tical depth to loss of heat, and at one mile down have to go more feet 
to gel it. And let it not be forgotten that these results have been 
given us by men who are pledged to the opposite view, who would 
rather not have known these truti^s, and perhaps would have hid 
ihem if they could. It is possible, then, that other causes than in- 
ternal heat may have caused a former higher temperature of the 
globe. But more of this anon. Suppose now the other case — that 
the average temperature of the whole earth was 15° less than it 
is now. What would be the result ? Glaciers in Wales and Scot- 
land again as once there were before ; ice-floes in the valley of the 
Thames and on the Norfolk shores driving up the beds of sand and 
mud into contorted strata, such as we have in the JMundesles clifis ; 
and icebergs dropping — if the occan-currents flowed on as once they 
did — boulders of Scandinavian and other foreign rocks on the midland 
counties and the northern regions covered by the Glacial drift. 
Miller has shown the heat of the sun to be not more than 14,580° 
Pahr., — the heat of the oxy-hydrogen flame, — and probably it is not 
much less. Now the surface of the sun is given as 12,500 greater 
than the earth's, an 1, therefore, taking the earth's surface as unity, 
we have the proportion of 12,500 to 1.* If, therefore, assuming for 
convenience the temperature of the sun as 12,500° (instead of 14,580° 
Fahr.),we suj)pose our earth to fall into the sun, w ithout igniting on 
its external side, the total amount of heat radiated from his surface 
would evidently be 12,490°, or reduced by the size of the earth by 
one unit of heat, giving the surface the equivalent of one degree of 
heat. 
But as the sun presents only one side to us, a loss of radiation of 
heat to tlie extent of two degrees would take place on the side of the 
sun to vvhich the non-radiani earth was attached. As the sun how- 
ever rotates on its axis in 25 days, every alternate fortnight or there- 
abouts the total temperature of the sclar rays would be 2° Fahr. less 
* Cousiderable confusion of ideas and a want of logic will be attributed to me in these 
articles if it be not distinctly borne in raiud that I adojjt popular ideas and popular 
phraseology only for the moment, and that it is not intended to work these speculations 
into any definite theory. If any delinite conclusions be arrived at, they will be jjiven as 
corollaries to these speculations, and not embodied in Ihem. For example, we speak now 
upon the dictum that the vokune of tiie sun is 1,400,000 greater than the earth, its 
mass being as 354,936 to 1, and its diameter as 882,000 to 8000, or IIU times greater 
than the earth. This gives the sun a mean density four times less than the earth, — a 
point we shall presently discuss, as it is very questionable if we ought to take the visible 
face of the sun, and his apparent sizo, in determining his density, because heated to the 
extent of nearly 15,000 degrees, and having, as astronomers declare, an exterior luminous 
photosphere; and, as Kirciihof and Eunsen have shown, a still exterior atmosphere of lu- 
minous incandesceut metallic vapour. The light-exhausted internal nucleus of burnt-out 
and probably solid material of the central core of our luminary is what we ought to con- 
sider as the actual globe of the sun, and which is what we should piopeily estimate tor 
his mass and density, at any rate for purpusts of comparison with our earlh. 
