140 
and as this compressed air must give out its heat if it is in 
contact with any body at a less tension, it gives it out to 
my hand or to the moisture exposed to it, which in the 
one case feels hot and in the other experiences an effect of 
of heat, namely evaporation. It is the column of air that is 
giving out heat, each ray that pierces it squeezes it and 
squeezes out of it a certain amount of heat which we attri- 
bute directly to the sun’s influence, while in fact it is only 
mediately due to it. This I think satisfactorily explains 
the great and elementary difficulties of my position. I am 
not aware of any other difficulty which cannot be as easily 
met, and as I cannot see my way from escaping from the 
main conclusion at which I have arrived, I have ventured, 
paradox though it be, to present it for your criticism. To 
sum up this conclusion in a phrase, I hold that the earth 
receives no heat directly from the sun, the sun only supply- 
ing the contractile force which induces terrestrial heat. 
