144 Correspondence—-Mr. R. D. Roberts. 
and snow. If this means that the snow will not be melted easily, 
because it cools the air, there is self-contradiction. Snow can only 
cool the air by abstracting heat from it, and if snow takes up the 
heat, the heat is spent in melting it. As for what is said about cold 
rendering air diathermatous, so much the better for the melting. If 
the sun’s rays can readily pass through the air, they will the more 
readily reach the snow which they have to melt. These paragraphs 
are not worthy of the book.” 
Has not Mr. Hill misapprehended Dr. Croll’s argument ? 
It appears to me to be of this kind. Regarding climate as the 
average condition of the atmosphere in respect to heat, and con- 
sidering the atmosphere as in the main warmed, not directly by the 
radiant heat of the sun, but by contact with the warmed surface of 
the earth, then if under any arrangement of circumstances a portion 
of the earth’s surface can remain permanently at a low temperature, 
the air in contact with that portion of surface (7.e. the climate of the 
region) will also be permanently cold. 
Now since the heat that goes to melt snow and ice disappears as 
sensible heat and produces no rise in temperature, we have a case in 
point—a permanently cold surface—in regions covered with snow 
and ice as long as any of the frozen water remains unmelted. The 
presence of accumulated masses of snow and ice in any region 
would therefore result in a far colder climate than might be expected, 
taking into consideration only the amount of heat received from the 
sun. For as long as the temperature of the air is 52° F. or lower, 
whatever aqueous vapour falls will fall as snow, not as rain; there- 
fore, while snow and ice remain, accumulation will probably not 
cease, even during the summer. Moreover, although the aqueous 
vapour coming from warmer regions, on condensing and crystallizing 
into snow, gives out heat, will that heat avail to raise the general 
temperature of the air above freezing-point? Will not much of it 
be lost into stellar space? 
To sum the matter up, it is clear that if by some natural process 
the heat received in polar regions could be transmuted into some 
other form of energy, while that received in equatorial regions pro- 
duced the ordinary heating effects, very different climatic conditions 
would prevail, even if it were possible that the actual amount of heat 
received in the two regions were the same. In snow-covered 
countries the bulk of the sun’s heat received goes in the work of 
melting snow and ice, and produces therefore no effect in ameliorating 
the climate. R. D. Roserts. 
Jan. 21st, 1880. 
Ws regret to record the death of Professor Baron von Seebach, Director of the 
Geological Museum, Gottingen. He was not only eminent as a man of science, but 
endeared by ties of warm friendship to a large circle of friends, who will deeply 
deplore his loss. 
Erratum.—In Mr. Clement Reid’s paper, ‘‘ The Glacial Deposits of Cromer,” 
Gxou. Mac. Feb. 1880, at p. 56, the bracket for ‘ Lower Glacial’ should not include 
the ‘ Forest Bed.’ - 
