A. E. Verrill— The Bermuda Islands; Geology. 55 
But their summits are now too far below sea-level for the growth 
of reef corals, though a few small corals are found on them. 
The nearer is the Challenger Bank. It lies 13 miles 5. 50° 14’ W. 
from Gibb’s Hill light. It is about 10 miles in circumference. The 
distance from the 100 fathom line of Bermuda to its inner edge is 
not over four miles. 
These two peaks and Bermuda are connected together by a ridge, 
covered with water only 580 to 690 fathoms deep, while the sur- 
rounding sea, on all sides, is from 1500 to over 2000 fathoms deep. 
The submerged slope of the Bermuda Mountain, on the north side, 
is steeper than that of any known large volcano upon the dry land. 
It falis off 1250 fathoms in 6 miles; that is at the rate of about 
1250 feet to the mile. The slope of the Argus Bank is, on one side, 
7620 feet in 10 miles. (See fig. 7.) 
No doubt each of these peaks and craters, when they were most 
active, rose high above the level of the sea, like the volcano of 
Teneriffe, though not so large or high. Perhaps more like Marti- 
nique, St. Lucia, and Dominica Island, among the Antilles. The size 
was similar to some of the latter, and there may have been many 
eruptions as violent as the recent eruptions of Mt. Pelé and from as 
lofty a crater. In fact there must have been very many great erup- 
tions to have built up such an immense cone from the bottom of the 
deep ocean. 
After the volcano became extinct there followed a vast period of 
time during which the action of the sea undermined and _ levelled 
down the materials of the volcanic cones, filling up the-craters, more 
or less completely, at the same time, in case any deep central pits 
remained. This period of erosion may have lasted through all the 
Jurassic, Cretaceous, and Eocene periods, with more or less oscilla- 
tions of level. However, it is probable that during those periods 
more or less extensive reefs of corals and deposits of shell-sand were 
formed, for during the Jurassic period reefs of corals existed as far 
north as middle Europe, and the climate in the latitude of Bermuda, 
in the Cretaceous and Eocene, must have been much warmer than at 
present. In any case, the final result of the erosion of the larger 
volcanic cone must have been to form submerged banks or shoals at 
a suitable depth for the abundant growth of corals, mollusks, etc. 
It is probable that direct erosion by the sea waves would not have 
cut down the cones very far below the level of low-tide, for the 
waves in storms of ordinary force have little erosive power beyond 
20 or 30 feet deep. In violent storms the wave action may have 
