A. E. Verrill— The Bermuda Islands; Geology. 59 
If the higher land had become covered with luxuriant vegetation 
in the pre-Glacial times, this eventually would have had the effect of 
diminishing the accumulation of sand on the higher dunes. The 
drifting of the sand would have been more and more restricted to 
the vicinity of the shores, and therefore the bays and inlets would 
have been filled up more rapidly, except in face of strong currents. 
It is not unlikely that the Bermuda cedar and the palmetto (which 
last is peculiar to Bermuda), with other trees now extinct there, may 
have then formed dense forests over most of the land, similar to 
those that existed when Bermuda was first discovered by Europeans. 
Indeed, from the great size and abundance of the fossil land snails, 
on small islands now barren and nearly bare of vegetation, it is 
evident that there was a former period when the climate was more 
moist and the vegetation much more abundant than in the present 
period. It is known that the Pliocene was really a period of greater 
elevation than the present, for I have myself found the large fossil 
land snails (P. Nelsoni, pl. xxvi) in limestone strata of the Walsing- 
ham period, in places now submerged beneath the sea. It is said 
to have been found in the limestones at the depth of about 48 feet 
below the sea at Ireland Island. 
7. Bermuda in the Glacial Period. 
That the advent of the Glacial period caused a marked change in 
the climate of Bermuda cannot be doubted. Huge continental ice- 
sheets existed over the whole of New England, Nova Scotia and 
Newfoundland, and their lofty frontal ice-cliffs, extending for 
hundreds of miles along the coast and reaching some miles south of 
the present shore lines, were dropping vast numbers of icebergs, 
doubtless of gigantic size, like those of Greenland, into the sea con- 
tinually. Those ice-cliffs were not over 625 miles north of Bermuda, 
and doubtless the icebergs drifted much nearer. Possibly the Gulf 
Stream was stronger than now. If so, the icebergs may not have 
crossed it, but they must have gone far southward in the inshore 
_ Arctic current.* 
* In a former article (Amer. Jour. Science, ix, May, 1900), I suggested that 
the marine climate in the glacial period might have been warmer than now, 
because of the occurrence of fossil West Indian shells that no longer live there. 
But with the exception of Livona pica (tig. 60) carried inland by the hermit 
crabs, no marine fossils are known from the rocks that I now consider as pre- 
glacial and glacial. The beach formations, containing most of the marine shells 
