‘ 
56  E. Desor on the Post-Pliocene of the Southern States. 
ground that the boulders did indeed i the limits of the | E 
ancient glaciers. On closer examination it was found, however, 
that the glacier theory could not apply to the Pen under con : 
sideration, in as far as the materials which underly the boulders — 
are not only stratified, but moreover contain a quantity of fossil — 
remains, which indicate that a considerable amount of time must 
have elapsed between the furrowing of the rocky floor and the 
transportation of the surface boulders. Now if the furrows and 
scratches have been made by glaciers, it is evident that the boul- 
ders.resting on the surface of the stratified sand must have been — 
transported at a much later period. In the glacier theory of M. 
de Charpentier (which is also advocated by M. Agassiz) it is as 
sumed on the contrary that the furrowing of the rock and the 
transportation of the poe are simultaneous, that they are the 
result of the same agency.* 
The third and most popular theory is that which decries * 
spas aay of the boulders to the agency of ice rafts. Whe 
we consider the striking contrast which exists between the cia 
of the bon ides and the minuteness of the materials on which 
they rest, which excludes all idea of their having been assorted, 
and consequently of all violent action, there is indeed sufficient 
reason to look upon this theory as the best adapted to solve the 
problem. Supposing the boulders to have been packed in ice 
which was driven by wind and current from north to south 
along the coast, it seems natural that these rafts should have beet 
stranded upon the prominent points of the coast and adjacent 
islands which at that time were shoals, dropping ter their but 
den of boulders. 
here is, however, a difficulty even in this theory; viz., the 
gircumstatice that the ice-rafts must have reached deg eee a8 
far south as New York, whereas at the present day it is very 
seldom that they ate driven as far south. + ‘To assume af the 
* Whether the furrowing and polishing of the rocks is really the result of glaciet 
action, and whether the materials of the stratified clay, sands and gra vel-deposits 
were first tran by ee and afterwards m mee dis ‘acres 
waft bergs have been seen as far south Se 
