116 W. J. MeGee—Theory of Glacial Climate. 
mgr In the preps n theory, per se, then, all save 
the immediate effects of increased eccentricity, under condi- 
et similar to those saa known to obtain; must be elimi- 
nated ; and on these further premises may the mode and rate of 
iee-accumulation be sou 
n the north-frigid zone ‘the existing ice-fields are to all ap- 
pearances permanent; whence annual addition to them from 
congealed precipitation and loss from melting, flow of ice and 
water, and the liberation of bergs are practically equal. The 
annual precipitation can only be approximately estimated. If 
on the last edition of Loomis’ rain chart’ the precipitation on 
land areas be the means of the values represented by the several 
tints employed, the average for the year at N. lat. 68° is 13°3 
inches. Toward the pole it must be paiekally less: it is, 1n- 
ed, sometimes so little in northern Greenland that Bessels 
thought the glaciers there must be but remnants of those formed 
during past ages.” The mean (and the measure of melting) 
for the whole year certainly cannot exceed 10 inches. 
Neglecting trivial amounts from diverse sources, the heat 
reaching the frigid zone is derived (1) from vapor-laden winds, 
and (2) from direct solar accession. Now that received from 
the first of these sources is indeterminate; but that from the 
second is alone sufficient to liquefy 399 inches (83°26 feet)” 
annually. Actually not more (and probably far less) than 
zy of this melting can take place, and it is hence manifest that 
m computing the ‘effects of rae ii the actual and not the 
theoretical values of annual addition and loss must be em- 
loyed.” The source of the preter eae need not here be con- 
sidered in detail. 
For convenience, and since no appreciable error will be intro- 
duced thereby, the foregoing — for precipitation and melt- 
ing, and their equality, may be assumed normal—i. e., such as 
would obtain were the solstices eddidiaant from the apsides. 
Different investigators hate shown that the immediate result 
of increased eccentricity ri soaatrcie with precession) must 
This Journal, xxv, January, 1 
17 Cited by Woeikof, oo of eo Globe,” Smithsonian Contrib. Knowl., 268, 
weet Bigibs 1876), 6 
“ Maximuni ‘Synchronous Glaciation,” ae cit., 473. 
in force, and greate agence must be sheeted re: the agencies contemplated in the 
ecce: eory. 
19 Tp the discussion already alluded to (*+On the Superficial Deposits of the Mis- 
sissippi neat Geol. uae vi, 1879, 418) the theoretical rate of et was 
used as is 8 for an estimate of the maximum removal of ice during an inter- 
and the laste is accordingly far too large. 
