Wright.] 
434 
[Jan. 1, 
for the cutting of the present canon of the Snake river through 
these lava flows, by the rate of recession of the various falls. 
While I am, as you see, unable to give any definite estimate of 
the age of the beds from which the image is supposed to have been 
derived, I regard them as probably of far greater antiquity than 
any deposits in which human implements have hitherto been dis- 
covered. If, as I am now inclined to think, they antedate the 
cutting of the present canon of the Snake river through the great 
lava plains, their antiquity at once becomes very great, as is shown 
by a comparison of the conditions which prevail there with those 
of the Niagara river, whose rate of recession has been so closely 
determined. The gorge of the Niagara has been cut through lime- 
stone and shale for seven miles to a depth of not over three hundred, 
feet. The Snake river from its entrance into the lava fields at Amer- 
ican Falls to Shoshone Falls, a distance of one hundred to one hun- 
dred and twenty miles, has cut a gorge in hard basalt from seventy 
to four hundred feet deep, and below Shoshone Falls, for an un- 
known distance, a gorge six hundred feet deep in similar material. 
In the present state of our knowledge I find it difficult to insti- 
tute any comparison whatever between these deposits and the gold- 
bearing gravels underlying the lava flows of California. Compar- 
ison between so widely separated regions are hypothetical, unless 
based on such an intimate knowledge of the geological structure 
of the intermediate region as can hardly be arrived at in the pres- 
ent generation. That instituted by Mr. Becker with the gravels of 
the Upper Boise basin has a slight basis of probability if his prem- 
ises are reliable, but the connection between these and the Nampa 
beds remains yet to be determined. 
Regretting that I am not able to give a more satisfactory answer 
to your question, I am 
Very sincerely yours, 
S. F. Emmons. 
In reply to a letter requesting through Mr. Kurtz a statement 
from Mr. Duffes, and making other inquiries, I received the follow- 
ing : 
Nampa , Idaho Ter., November 7, 1889. 
Prof. G. F. Wright. 
Dear Sir : 
Yours of Nov. 2, just received. I enclose letter from Mr. 
Duffes as requested. 
