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. loss for 

 every 63 feet 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 get 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 truths, and perhaps would have hid 

 them 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 Mundesley cliffs; 

 and icebergs dropping — if the ocean-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° 

 Fahr., — 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, and, therefore, taking the earth's surface as unity, 

 w r e 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 suppose our earth to fall into the sun, without igniting on 

 its external side, the total amount of heat radiated from his surface 

 would evidently be 12,499°, 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 the extent of two degrees would take place on the side of the 

 sun to which the non-radiant 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 solar rays would be 2° Fahr. less 



* Considerable confusion of ideas and a want of logic will be attributed to me in iliese 

 articles if it be not distinctly borne in mind that I adopt 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 definite conclusions be arrived at, they will be given as 

 corollaries to these speculations, and not embodied in them. For example., we speak now 

 upon the dictum that the volume of the sun is 1,400,000 greater than the earth, its 

 mass being as 354,930 to 1, and its diameter as 882,000 to 8000, or 111§ 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 

 lace of the sun, and his apparent size, 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 Kirchhof aud Bunseii have shown, a still exterior atmosphere of lu- 

 minous incandescent 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 properly estimate for 

 his mass and density, at any rate for purposes of comparison with our earth. 



