MAN AND THE LAVA BEDS. 



'03 



be most readily furnish during the Glacial period, when the 

 streams of that region were swollen not only with the in- 

 creased annual precipation, but with the melting of the 

 glaciers which doubtless had for a long time occupied the 

 mountains near the head- waters of the Boise* River to the 

 north. Very likely, also, the lava-flows which obstructed 

 the river a few miles above Boise City turned its course to 

 the southward, so that it may have wandered for some time 

 over the plain in the vicinity of Nampa. 



Fig. 196 — Nampa figurine "and map "of the Snake river valley illustrating the text. 

 For photograph of the bowlder bed at Pocatello described in the text, see page 615. 



In addition to these general considerations we have here 

 a most interesting and suggestive special situation from which 

 much evidence may be derived in support of the foregoing- 

 interpretation of the facts. In the summer of 1890, while 

 making investigations in the Snake River Valley at Pocatello, 

 350 miles above Nampa, and where the elevation is 2000 feet 

 higher, I was confronted with an immense delta of bowlders, 

 many of them three and four feet in diameter, at a consider- 

 able distance from the foot hills of the mountains to the south , 

 which seemed inexplicable from any natural causes within 



