474 G. F. Becker—Influence of Convection on Glaciation. 
be precipitated below the isothermal line or surface characterized 
uring the same period by a temperature of 10°. His suppost- 
‘tions are two: that the atmosphere is saturated (unless special 
exception is made, which is not the case in his concluding 
remarks), and, as the results of a calculation that the difference 
in the velocity of the wind in the two periods is insignificant. 
Granting for the sake of argument the insignificance of the dif- 
ference in the velocity of the wind,* it is certain that, if the 
supposed complete saturation of the atmosphere would produce 
no essential alteration in the problem, Captain Dutton’s result 
is immediate and inevitable; but as complete saturation repre- 
sents an extreme case, it seems desirable to examine its bearing 
on the results. : 
No one of course would think of denying that the mean 
saturation of the whole atmosphere is never complete nor even 
the earth the rise of air bodies, and sometimes other causes, 
tend to chill the air below its dew-point, while at the same time 
* It appears to me improbable that the additional energy which a warmercli- 
mate am impart to the air currents would be disteibuted:simaply among existing 
