158 



If jou ask what els' the gravels and cl.iys can tell us that we mar 

 read for ourselves, I can mention then besides the arctic leda and 

 saxicava shells, and the Hudson Bay fish of Green's Creek, belonging 

 to the flood poriod re'erred to, the leaves and woods and Tnammalian 

 bones of the more ancient rivers to which I have referred as genei'ally 

 biirietl out of sight by the boulder clays and the leda clays. The 

 U2')per courses of all these ancient streams were necessarily higher, and 

 in many places the debris whicli filled them must have been, since ex- 

 posed; sometimes accidentiilly, as in connection with coal mining in 

 Pennsylvania; in wells and borings, for coal oil, or salt, or other 

 minerals. Exposures may exist where our eyes have not learned to 

 read them. As you know, a milder climate than the present preceded 

 the cold period and its flood phenomena. So it was on the Pacific 

 Coast, in Greenland, and generally in northern America and Europe 

 during the middle and later tertiary. 



River gravels of pliocene age ante-dating the present mammalian 

 creation the genus liotno only excepted have been abundantly ex- 

 posed and identiSed in the auriferous gravels of the P.icific Coast. 

 They are filled up river valleys like ours, which have been i-e-excavated 

 by natural operations, and sifted by men in quest of gold with a 

 thoroughness no other quest could ever have accomplished. During 

 the years 1869, 1870, 1871, it was my lot to be engaged in their study, in 

 connection with the Geological Survey of California. Leaves, woods, 

 mammalian bones and human relics, consisting of implements and 

 bones were industriously collected. The j)lant life was thoroughly 

 studied, and reported on by Leo Lesquereux w^ho stands at the head of 

 the vegetable biologists. Their i)Hocene age has been established, and 

 the facts have been accessible to all men in published form have lain, 

 in fact, in the public libraries of Ottawa for a dozan years. An article 

 in the Overland Monthbj, written hy myself about 1873, which 

 described a prolific find of mortars and p stlcp in a mountain of basalt 

 covered gravel, with a precision not to be escapi^d from, had a wide 

 popular circulation and has slept on the shelves (.>f a hundred libraries. 



To generous Louis Agassiz, and to the circumstance of his visiting 

 the Pacific Coast ;>t that time, the world is indebted for the machinery 



