508 



THEORIES OF THE ORIGIN OF THE GRAVEL. 



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sea, which was supposed to cover the country during the time of their accumulation. Against this 

 idea may be urged the conclusive objections : First, that the gravel is not of salt-water origin, no 

 marine fossils having ever been found in it, while the bones of land-animals are frequently found, and 

 the remains of trees and land-plants are plenty in it everywhere ; second, the internal structure of 

 the banks themselves is in general not such as is produced by the waves of a sea, but is precisely 

 like what running streams produce ; third, the manner of distribution of the gravel over the sur- 

 face of the country is not only entirely unlike anything that a sea could produce, but is so far re- 

 moved from it that it is hardly possible to imagine any natural cause or combination of causes 

 which, even by redistribution, could have brought about the present state of things, if the gravel 

 had been originally spread beneath a sea; fourth, the idea that this work was accomplished by 

 either a salt or a fresh water sea involves of necessity the additional idea of the subsequent up- 

 heaval of the mountains, — an idea in favor of which there is not a particle of evidence, so far as I 

 know, while there is the strongest proof against it. No sea, however deep, could spread such 

 gravel in such a way through a range of not less than six thousand feet of altitude, over the 

 Hanks of even a submerged mountain-range, resembling in form and outline the Sierra Nevada of 

 to-day. 



Another theory which has been broached, I believe, with reference to the ancient gravel is that 

 it was the direct work of glaciers. Aside from the fact that there is not a particle of evidence to 

 support this idea, nor any positive evidence, so far as I know, that glaciers ever existed in any 

 part of the Sierra at a period so ancient as this, nor any proof that even in their greatest develop- 

 ment in later times they ever extended, as the ancient gravel does, to the foot of the range or 

 anywhere near it, — aside from all these facts, it is probably a sufficient answer to such a theory 

 to mention the fact, so palpable everywhere in the gravel region, that the whole character and 

 structure and distribution of these gravel banks is utterly unlike anything that glaciers ever pro- 

 duce, but is exactly like what we may see produced to-day, wherever circumstances favor it, by 

 streams of fresh and running water. 



Against any idea that the gravel can have been distributed by floating ice, dropping its debris as 

 it melted, may be urged almost all the objections which hold against seas and against glaciers com- 

 bined, together with other and no less potent ones peculiar to itself. 



In fact, wherever we go throughout the gravel region, the evidence constantly presented is cumula- 

 tive and overwhelming, that these gravel banks are really the work of streams of fresh and running 

 water. And so much as this has, indeed, been from the earliest times the accepted belief of all 

 well-informed observers who have had any opportunity of studying for themselves the ancient 



gravel.* But yet the great questions remained unsolved, — Whence came these streams, and where 

 did they go 1 



In answer to these questions, the theory which first gained extensive credence was that of the 

 former existence of a single great river, flowing southeasterly for hundreds of miles along what is 

 now the southwestern slope of the Sierra, and nearly parallel with the axis of the range, before the 

 mountains were uplifted. And the supposed channel of this great stream, now filled with gravel, 

 was called the "blue lead." 



This theory was founded, of course, upon the supposed existence of a narrow belt of deep gravel 

 banks, stretching across the country in a southeasterly direction. But later, when it came to be more 

 generally understood that the deep gravel banks were not all confined within so narrow a belt as 

 this theory would require, the theory was modified far enough to admit the existence in the gravel 

 period of two or three large rivers with their branches, the courses of the main streams, however, 



* Mr. Goodyear had not taken pains to make himself acquainted with what had been published in regard to the 

 Gravel Region, or he would not have written the above paragraph. If the reader will compare what is stated in a 

 previous chapter in regard to this point (see pages 66-72), he will see that the theory of the marine origin of the 

 gravel deposits was the one adopted by most, if not all, of the professional geologists who had examined'the Sierra 

 Nevada previous to the beginning of the work of the Geological Survey, especially by Messrs. W. P. Blake, Laur, 

 and Hector. — J. D. W. 











