30 The American Geologist. JuIy l9oa 
was equable and temperate, or even warm. In all latitudes 
from which Corniferous fossils have been brought apparently 
a warm and genial sea extended from central North America 
Ear away to the Arctic region. 
This interesting but obscure subject of ancient climate 
warrants a slight digression. If the whole earth was then 
maintained, by some as yet unknown means, at an almost uni- 
form temperature the problem is solved. But, without postul- 
ating so vast a revolution of the present order of climates, a 
suggestion may render so striking a departure from existing 
conditions a little less difficult of credence. If, as some geol- 
ogists maintain, the mid-American sea was open to the south 
and the configuration of the land in that direction was such 
as to allow- the deflection of the great equatorial current to 
the northward, then this current must have found its outlet 
along the wide northeastern channel of St. Lawrence, as it 
may well he called, and by another, perhaps still wider, to the 
northwestward into the Arctic regions, which may be called 
the Mackenzie channel. By this means the heated waters of 
the equatorial Atlantic would be carried to the northeast and 
perhaps into the European seas and to the Polar ocean, bear- 
ing with them a mild and genial climate and utterly preventing, 
the accumulation of snow and ice. On this view a coral-bear- 
ing sea may have existed as far north as Xorth Somerset, in 
which frozen and forbidding region Devonian fossil corals 
have been found. Nor is it improbable that conditions were 
such as to intensify the strength of this Corniferous gulf- 
stream and so to raise its initial temperature above that of its 
modern representative, which, at Cape Sable, is 80° F. Even 
now the latter by it> abnormal warmth has girdled the Bermu- 
das with coral reefs in 33° of north latitude, far to the north 
of the usual limit of the growth of reef-building polyps. 
Finally, what was the duration of the Corniferous period? 
The rate of the growth of coral, which is the most important 
element in this problem, is very uncertain. Equally so is the 
rate of the accumulation of coral-mud. But on any view there 
is no doubt that both are exceedingly slow. Dana thinks that 
six inches in a century is a fair average. LeConte, resting 
011 some observations of Agassiz. adopts an estimate four times 
a- great. If the accumulation of coral sand and mud, of which 
