W. SJ. MeGee—Theory of Glacial Climate. 117 
be the inauguration of five glaciation-factors, of which two are 
direct and three indirect. These are, (1) diminution of mean 
ranted. It must therefore suffice to assume for all a probable 
value ;* and it will assuredly do no violence to the most con- 
servative opinions (especially in view of the considerable influ- 
ence shown to be exerted by the first factor) to assume that the 
united agency of the five factors is such as to counterbalance 
the lessened solar distance in summer, and render the combined 
factors effective in the sum of the excess of winter-season above 
period, accordingly, the annual accumulation of ice was 
$3 X10, or -185 inch, and within which the total accumulation 
was equal to -185 13,000, or 2405 inches (200 feet) 
Toward the equator actual and possible annual precipitation 
and liquefaction progressively increase, the first four glaciation- 
ay The writer, “A Contribution to Croll’s Theory,” this Journal, xxii, 1881, 437. 
Hill, “ Evaporation and Eccentricity,” Geol. Mag., viii, 1881, 481; this Jour- 
nal, xxiii, 1882, 61. 
Croll, * Climate and Time,” 1875, 58; Geikie’s Text Book,” 1882, 25. 
cit. 1, 60; op. cit. 2, 26. 
t it be clearly understood that such an assumption is not made as an attempt 
to demonstrate the validity of the eccentricity theory by any process of defective 
reasoning; the only demonstration worthy of the name, now admissible, would be 
an approximate evaluation of the glaciation-factors, severally and jointly, at 
_ various latitude of the zone over which they are efficient. Such an investigation = 
i d req prose- 
Presents no serious difficulty aside from the time and labor requi 
oo. 36 “Climate and Time,” 320. 
