TRANSACTIONS OF THE SECTIONS. 113 
which in the author’s opinion mark so many levels, at which the waves 
of the sea encroached for a long period. There are also above the 
summit of all the cliffs, three distinct parallel terraces and as many 
cliffs, each about four feet high, which sweep round a small combe in 
a semicircular form, like the seats of an amphitheatre. 
If we then descend the river from Vatteville to a place called Sen- 
neville, we meet with a singular insulated needle, about fifty feet high, 
perfectly isolated on the escarpment of chalk on the right bank of the 
Seine. 
The third or last range of inland cliffs referred to, is situated 
about twelve miles below on the left bank of the Seine, beginning at 
Elbceuf, and comprehending the Roches ‘d’Orival. Like those before: 
described, it is in part overhanging, exhibits a white powdery sur- 
face, and consists entirely of horizontal chalk with flints. Its base 
is only a few feet above the level of the Seine, its height in some 
parts exceeds 200 feet. It is broken in one place by a pyramidal mass 
or needle, called the Roche de Pignon, which stands out about twenty- 
five feet in front of the upper portion of the main cliff, with which it is 
united by a narrow ridge about forty feet lower than its summit. Its 
height is about 200 feet, and like the detached rocks before mentioned 
at Senneville, Vatteville, and Andelys, may be compared to those 
needles of chalk which occur on the coast of Normandy, as well as the 
Isle of Wight and in Purbeck. 
The author then states, that while there are in some places marks of 
cliffs and terraces at six or more distinct levels, there is sometimes only 
one range of cliff, which may be either a few feet, or more than 200 feet 
in vertical height ; and on the other hand, there is often no outbreak 
of bare rock or precipice, as is well exemplified in that part of the 
valley where the Cote des Deux Amants faces that of Pont St. Pierre. 
The cliffs, where they do exist, are usually confined to one side of the 
river, whether on the right or left bank. Various causes are assigned 
for this partial occurrence of cliffs, and the variety of their number and 
elevation where they exist. It is assumed that the valley of the Seine 
was excavated by the waves and currents of the sea, during the slow 
and probably intermittent upheaval of the land. When the denuding 
operations therefore were in progress, the valley constituted the chan- 
nel of the sea between two islands or opposite coasts. Considerable 
cliffs would be formed at those points only against which the waves 
and currents set with peculiar force. Being thus originally partial, 
they subsequently became more rare by the obliterating action of frost 
and rain. A series of smaller cliffs would often be united into one 
when the undermining force of the sea caused it to encroach greatly at 
a certain point.* 
On Glaciers and Boulders in Switzerland. By Professor AGASSIZ. 
M. Agassiz particularly drew attention to facts relative to the man- 
" ner of the movements of glaciers, which he attributes to the introduction 
and freezing of water in all their minutest fissures, whereby the mass of 
1840. I 
