McGee—Meridional Deflection of Ice-Streams. 889 
The whole of the solar energy reaching the ice-stream will 
not, however, be utilized in affecting its condition ;—a consider- 
able portion will be lost by direct reflection; and of the 
remainder the discordant (and hence heating) rays will have 
been in part absorbed by the vapor of the superfluitant atmos- 
phere ; but the diminution will be proportional. 
Again, an important share of the heat absorbed by the 
glacier will be derived from the surrounding air, from the 
earth beneath, and, by reflection and radiation, from contigu- 
ous earth, rocks, hills, ete.; and this share will be pretty nearly 
equally distributed over the entire surface. If half the effec- 
tive heat reaching the ice comes from such. sources, the ratio 
of effective energy received by its respective halves will be 
teduced to 25773: 17320. 
Also, the differential accession of the two halves will be 
ounteracted to a considerable but indeterminate extent by 
terior conduction. If the unequal distribution be thus 
diminished by a half, the ratio will be further reduced to 
23660 : 19433. 
Ow, as empirically shown by innumerable observations, and 
#s theoretically indicated by ali plausible hypotheses of glacier 
Motion, the rate of movement of ice-streams varies irectly 
with the heat-accession or with some slightly variant function 
of that element. If, then, in the assumed case, the accession 
© Incompetent to occasion loss by melting (i. e., if on any sec- 
tion of the stream daily accession equal nightly radiation), all 
Will be effective in producing movement, the two 
tend to flow at rates varying with the accession, and the stream 
em hence tend to curve in the direction of the slow-moving 
Side, 
Such tendency will be counteracted in part by (1) the mobil- 
ity of the ice (which will permit the southern half to the more 
readily spread laterally and to slip 2 
(2) by the dfriee | | : 
ton encountered with lateral shift- * 
ing of the stream. Accordingly, 
the loci of flow in the determined 
ratio will lie somewhere wines the 
If the direction of flow depart from the parallel, other ele- 
Ments are introduced. To facilitate their comprehension, let 
