Mineralogy and Geology. 117. 
height of the snow-line (Mrs. Somerville’s ‘Physical Geography,’ 
p. 61) is about 6000 feet. On the Straits of Magellan, on the con- 
trary, though the mean temperature is several egrees above 
freezing, the height of the snow-line (see table) is little more than 
half as much. 
It is well known that, other things being equal, the magnitude 
of glaciers depends on that of the snow-fields in which t ey rise; 
nd as of course any depression of the snow-line will enlarge the 
snow-field, it follows that the lower the snow-line the further will 
the glaciers descend below it. Asa decrease of about 3° F. is due 
on the climate of Central Europe, but it would have a very great 
effect in those high latitudes where the glaciers would reach the 
of fi 
And again, p. 243 :— 
“Tt is exceedin ly probable that a diminution of the temperature 
ths b only would at once place one-fourth 
a little would plunge a great part of the country under a mantle 
Trost,” Bem: 
ita 
5S 
Into the head of every fiord in western Norway. . . . 
lowering of the snow-line over so large a surface would deteriorate 
the Snow-line still further. 
perature. 
wing data from Mr. Croll’s paper. The recently 
in the old determinations of the sun’s distance 
affects both distances alike, and consequently does not affect their 
ratio, Along with the maximum distances of _the sun at present 
ind at greatest eccentricity, I state the proportionate quantities of 
heat the earth will receive under those two different conditions :— 
Sun’s ee ‘ Ratio of heat 
At present SESS 6 2.6 8 3 aoe 96,473,205 miles cer 100. 
- t greatest eccentricity.. 102,256,873 “ ‘cee, 90 
