R. W. McFarland—Perthelion and Eccentricity. 105 
and full of aqueous vapor, absorbing the heat saeco from the 
snow, the snow-line would, in this case, undoubtedly descend 
to a lower level on the dry than on the moist side. No doubt 
more snow would be evaporated off the dry than off the 
moist side, but melting would certainly take place at a greater 
elevation on the moist than on the dry side, and this is what 
—— on them i8 great, but because the quantity melted is 
all. nd the reason why the snow does not melt is not 
reno the amount of heat received during the year is not 
eis to the work of melting the ice, but mainly because 
the dryness of the air, the snow is prevented from rising to 
the melting point. 
There is little doubt but that the cold of the glacial epoch 
would produce an analogous effect on temperate regions to that 
experienced at present on Arctic and Antarctic regions. The 
cold, although it might, to some extent, diminish the snow fall, 
woul ry the air and prevent the temperature of the snow ris- 
the first lads the upper surfaces of the clouds act as reflectors, 
throwing back the sun’s rays into stellar space, and in the second 
place, of the heat which the clouds and fogs absorb, more than 
one-half is not radiated downward on the snow, but upward 
into space. nd the comparatively small portion of heat 
which manages to reach the ground and be available in melting 
the snow is insufficient to clear off the winter’s accumulation. 
Art. XIV.—Perthelion and Eccentricity ; by R. W. McFar- 
LAND. With Plate IIL 
THE following table gives the longitude of the perihelion and 
the eccentricity of the earth’s orbit for a period of 4,520,000 
years, of which 3,260,000 are before 1850, and 1,260,000 after 
1850. It is computed by the formule of LeVerrier, as quoted 
