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Pacific States we do have true Lacustrine Sedimentary 
deposits, but they invariably are made up of totally-different 
forms of Diatomaceze from those to be seen in the Sub- 
Plutonic material. In all cases they are such species as live 
at the present time in small collections of water and are of 
much more recent formation than the Sub-Plutonic Strata. 
Another point requires treating of, and that is the forma- 
tion of the cafions of the Pacific States. It is generally 
supposed and, I believe, on all hands accepted, that these 
have been gradually cut down through the hard Trap and 
Lava, by the action of the streams themselves. Now there 
are one or two facts in this connection which it will be neces- 
sary to bear in mind, first, to have such a cutting down 
action the streams should rise from a high section of country, 
and then flowing in such valleys as were ready formed for 
them, should follow their direction until they made their 
way into the ocean. Again the kind of rock through which 
such a wearing action by water takes place, must be con- 
sidered. The best studied case of this kind which is 
undoubtedly due to the wearing action of water, is that of 
the Niagara River and Falls. We find the facts here stated 
in the following terms by Dana, (Manual, page 590). ‘“ The 
Niagara has made its gorge by a slow process of excavation, 
and is still prolonging it towards Lake Erie. Near the fall 
it is 200 to 250 feet deep, and at the fall itself 160 feet, the 
lower 80 feet shale, the upper 80 limestone. The distance 
from Niagara to the Queenstown heights is seven miles. If 
then the fall has been receding six miles, and we can ascer- 
tain the probable rate of progress, we may approximate to 
the length of time it required. Hall and Lyell estimated the 
average rate at one foot a year, which is certainly large. 
Mr. Desor concluded, after his study of the falls, that it was, 
“more nearly three feet a century, than three feet a year.” 
Taking the rate at one foot a year, the six miles would have 
required over 31,000 years; if at one inch a year, which is 
8} feet a century, 380,000 years. It must be remembered 
that the Niagara has had to work its way through only com- 
paratively soft shale and limestone; what time shall we assign 
