Shaler.] 
262 
[March 4, 
Desert hills. It is there clear that the sea remained in contact 
with the land for long periods at three different stages above the 
present level of the sea. The highest of these distinctly indicated 
benches is at an elevation of 300 feet above the present high tide 
mark. At that point, wherever the attitudes of the rock were 
favorable for marine action, the sea excavated a bench in the firm 
granitic material which is about as extensive as that which it has 
produced along the present shore line. At certain points this 
bench is cut back more than 200 feet from the original point of 
contact of the waves with the shore line, an amount of excavation 
which is very rarely, if ever, found along the existing coast line. 
At about 240 feet above the sea is another bench also deeply ex- 
cavated in the manner indicated in the above cited memoir. 
Again at about 90 feet above the sea is a third and less consider- 
able bench. The aggregate work done at these three levels is 
several times as great as that accomplished along the zone now 
attacked by the sea. After the formation of the lowermost of 
these benches the succeeding elevation of the land lifted its sur- 
face above the level of the present sea-shore. It evidently dwelt 
at that height for a considerable time as is indicated by the fact 
that extensive forests and jinorasses now submerged had time for 
their development. The amount of cutting done at this lower 
level is unknown for the reason that this bench is now submerged. 
Leaving out of account the somewhat doubtful work of the sea 
along the New England coast above the level of 300 feet, we thus 
have proof for as least four well developed coast lines marking 
levels of the sea before the present station was acquired and in- 
cluding the present coast line the total number of benches is not 
less than five. Whoever will attentively study the erosion 
on the present coast line will I think become satisfied that the 
time required for the accomplishment of the work of the waves 
and tides on the present horizon cannot well be less than 5000 
years. If we consider only the growth of the marine marshes 
which are formed in the reentrants behind the sea margin, it 
seems necessary to allow at least this duration for the present 
shore level. I am therefore disposed to conclude that any such 
period as 10,000 years would hardly be sufficient to accouut for 
the marine work done along this coast after the burden of the ice 
was removed from it. 
