Searles V. Wood—The Cause of the Glacial Period. 297 
of Mexico, and hardly that hemisphere at all, now pours its heated 
water into this Gulf; and there, and also as it issues thence and 
runs northwards along the east side of America, before flowing away 
from that continent to Europe, it gives off the vapour which is pre- 
cipitated on the eastern side of the United States. This precipitation 
is greatest in the States surrounding the Gulf, where the annual fall 
ranges between 45 and 60 inches. From these there stretch north- 
wards, in the order of their names, the States of Georgia, the two 
Carolinas, Virginia, Maryland, Delaware, New Jersey, Pennsylvania, 
New York, the five New England States and Maine. The northern- 
most of these, viz. Maine, New England, and New York, embrace, 
with part of the Dominion of Canada, the eastern and south-eastern 
side of the St. Lawrence, or Lake basin; and with that Dominion 
are glaciated; the eastern extremity of the glaciation reaching the 
Atlantic from Newfoundland to the mouth of the Hudson. The 
States, or portions of States, which embrace the same side of the 
basin, south and south-west, and all but the extreme southern and 
western parts of the country lying between the great lakes and the 
Missouri river, together with so much of the rest of the Dominion as 
forms the northern side of this basin, are glaciated also, the north- 
western extremity of the glaciated area extending into the region of 
the drainage to Hudson’s Bay, by way of Lake Winnipeg.’ Though 
its northern extension is as yet unknown, the southern and western 
limit of this glaciated area appears to have been well worked out 
within the United States boundary.’ 
This great basin of the St. Lawrence and the Lakes was filled 
with land-ice so thick, as to override the parting between the 
drainage now flowing to the St. Lawrence and that flowing to the 
Mississippi, as well as that between the drainage now flowing 
to the St. Lawrence and that flowing by various rivers in the 
New England States, and in the country north of them, and by 
the Hudson, Delaware, and Susquehanna, direct to the Atlantic, 
enveloping as it did so the Catskill, Adirondack, Green, and 
White mountains (the highest of which last rise to more than 6000 
feet*), to their summits; but, with the exception of these mountains 
of relatively small extent and elevation, the whole of this area 1s 
comparatively low ground, nearly all of the Alleghany mountains 
lying to the south, and the much more elevated region of the Great 
Divide to the west of it. 3 
In this, I believe, all or nearly all of the American geologists are 
1 Dawson, Q. J. G. S. vol. xxxi. p. 620, e¢ seq. 
2 Insulated within this glaciated area, near to its south-western extremity, is an 
unglaciated space called ‘‘ the driftless area of Wisconsin,’’ due to the furcation and 
subsequent coalescence of this extremity of the ice-sheet as it issued to the Mississippi 
drainage region trom Lakes Michigan and Superior, which, as well as the other 
lakes, it filled. This small insulated area, as 1t does not concern my argument, 
I have not noticed in the text. 
2 Mount Washington, the highest (6,293 feet), has its summit, according to 
Hitchcock in Amer. Journ. 3rd series, vol. x. p. 383, covered with debris transported 
from distances of not more than three miles, but with ‘‘ Bethlehem gneiss’’ brought 
from a distance of twelve miles. 
