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hot, the moisture evaporates, &c. And this is true in a 
larger way of the superficial layer of the ground, which feels 
the intermittent effects of day and night, summer and 
winter, by absorbing more or less heat. How then do we 
account for this, for the heat must be absorbed from some- 
where, and the only practicable source is the direct sun- 
shine. My answer to this is very short. If we ascend 
through the atmosphere we rapidly find the temperature 
becomes lower, that as we get nearer the verge of the 
atmosphere, and therefore nearer the point where there is 
no atmospheric absorption of the solar rays we find the 
temperature to lower so rapidly that we are justified in 
concluding that if we could get outside the atmosphere 
altogether we should find the scorching of the hand, the 
absorption of moisture, and the various effects we attri- 
bute to heat reduced to a minimum, and are justified 
in concluding that if the envelope of the atmosphere 
were removed, if the earth were to be, such as the moon 
is, without an atmosphere, that its surface temperature 
would be but slightly affected by the direct sunshine. The 
effects of the sun’s attraction would be distributed through- 
out the mass of the earth, causing a general contraction and 
a general relative temperature with its focus at the centre, 
but there would be no surface layer of an aberrant and 
peculiar temperature, and few or none of the effects we now 
find in the direct sunshine. I argue, and I think I am 
justified in arguing, that these peculiar effects are due 
entirely to our having an atmosphere, to the fact of there 
being a medium between the sun and ourselves. If this be 
so, it is clearly most consistent with our contention, for the 
sun’s contracting force acts not only on the earth’s solid 
matter but on its gaseous envelope also, and in the latter 
case with much more powerful results. So that any surface 
exposed to the sunshine is exposed also to a column of air 
undergoing contraction or pressure on the part of the sun, 
