i88o.] 
685 
On Heat and Light. 
rays are stopped till the glass itself becomes hot ; or if we 
place a sheet of ice in the same position, the same result 
ensues till the ice is melted. On the assumption that the 
sun is throwing off heat like a fire, the thin air of the upper 
regions aCts like a sheet of glass or ice with this remarkable 
difference, that the heat never raises the temperature of the 
air, and yet (apparently, at least) it gets through it, as known 
to our consciousness on the earth’s surface ! the heat gets 
through, but not as the heat known to our senses, for 
Rumford showed that calorific rays can be passed through 
a vacuum without losing their temperature in the passage. 
The question of the temperature of the sun has been the 
subject of investigation by many scientists. Newton, one of 
the first investigators of the problem* tried to determine it, 
and after him all the scientists who have been occupied with 
calorimetry have followed his example. All have believed 
themselves successful, and have formulated their results 
with great confidence. The following, in the chronological 
order of the publication of the results, are the temperatures 
(in centigrade degrees) found by each of them : Newton, 
1,669,300°; Pouillet, 1,461°; Zollner, 102,200°; Secchi, 
5,344,840°; Ericsson, 2,726,700°; Fizeau, 7,500°; Water- 
ston, 9,000,000°; Spoerer, 27,000°; H. Sainte-Claire Deville, 
9,500°; Soret, 5,801,846°; Vicaire, i, 39 8 ° J Violle, 1,500°; 
Rosetti, 20,000°. The difference is, as 1,400° against 
9,000,000°, or no less than 8,998,600° ! There probably does 
not exist in science a more astonishing contradiction than 
that revealed in these figures. 
Another of the fallacies respecting heat upon which some 
curious theories have been founded as to the earth s future 
destiny, is that of assuming that all but its crust is a mass 
of liquid fire. In support of this intense central heat, it was 
at one time asserted that the temperature of deep mines 
invariably increased in proportion to the depth ; but doubts 
have, in late years, been thrown upon the statement. _ Still 
it is confidently asserted that the interior of the earth is in a 
red-hot molten condition, and that it is radiating its heat * 
into space, and so growing colder. One of the results of the 
Challenger and other explorations of deep ocean is to deter- 
mine that the water towards its bottom is freezing cold. 
Considering that the ocean covers nearly three-fourths of the 
entire globe, this faCb certainly does not support the theory 
of central heat accompanied by radiation. The coldest 
water, it is true, usually sinks by its greater weight towards 
the bottom, and that, it may be said, accounts for its 
coldness ; but, on the theory of radiation, the water of the 
