RADIATION AND ABSORPTION. 83 
24. It seems to me still necessary to indicate some of the 
most general consequences which result from these researches. 
The total quantity of heat which space transmits in the course 
of a year to the earth and to the atmosphere is deduced from 
the preceding observations: it is easy to see that this quantity 
of heat would be capable of melting upon our globe a stratum 
of ice of 
26 metres thickness. 
We have seen that the quantity of solar heat is expressed by a 
stratum of ice of 
31 metres. 
Thus, together, the earth receives a quantity of heat represented 
by a stratum of ice of 
57 metres, 
and the heat of space concurs in this for a quantity which is five- 
sixths of the solar heat. 
Between the tropics, the heat of space is only two-thirds of 
. the solar heat; for the latter is there represented by a stratum 
of ice of 
39 metres. 
It will excite astonishment doubtless that space, with its tem- 
perature of —142° below 0, can impart to the earth a quantity 
of heat so considerable that it is nearly equal to the mean heat 
which we receive from the sun; these results appear, at first 
sight, so contrary to the opinion which we form, either of the 
cold of space or of the power of the sun, that we shall be per- 
haps disposed to regard them as inadmissible. However, we 
must remark that, with regard to the earth, the sun occupies 
only five-millionths of the celestial vault, and that it must con- 
sequently transmit 200,000 times more heat to produce the same 
effect. 
In considering the phenomena under another point of view, 
we shall be led, on the contrary, to suppose that in these valua- 
tions the power of the sun is much exaggerated ; for if we ex- 
amine the temperatures instead of examining the quantities of 
heat, we arrive at this result :— 
That if the sun’s action were not felt upon our globe, the 
temperature of the surface of the ground would throughout be 
uniform and at 
—89°. 
Now, since the mean temperature of the equator is 27°5, we 
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