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HOW THE GRAVEL WAS ACCUMULATED. 



feet in depth ; but it seems hardly possible that any such gorges then could have been continuous 

 for many miles, and they were the results in all probability, not so much of denudation or erosion, 

 as of the original upheaving forces which built the range and raised the lofty peaks. 



Among these loftier summits the streams which slowly gathered the ancient auriferous gravel 

 took their rise. From thence they flowed southwesterly across the smoother sloping country, the 

 larger streams draining respectively nearly the same regions as now and in the same directions, 

 and finding their way by the shortest practicable routes to the valley, which, however, may then 



have been a lake or sea. 



These streams must have been rapid, too, as the grade was heavy for running water ; but the 

 velocity of their flow seems rarely if ever to have approached that of the modern rivers in a flood, 

 nor did they possess any such excavating power, because of the simple fact that they were not 

 confined in the bottoms of deep and narrow gorges, but, wandering through the rolling country, 

 were free, whenever their volume was large, to spread out over broader areas, their waters still 

 remaining shallow, or even to take new courses through adjacent hills. They were also, without 

 doubt, subject to freshets and droughts, as well as the modern streams, swelling at one time to 

 floods which might suddenly transport for certain distances large quantities of gravel of varying 

 coarseness, spreading it far and wide over their broad, pebbly beds, and again dwindling to far 

 smaller dimensions, or even to little rivulets, which might wander isolated here and there over the 

 expanse of gravel already accumulated, depositing only here and there little patches and bars of 

 sand. When a certain depth of gravel (a depth varying of course with every little detail of the 

 local topography) had thus been slowly accumulated in the original channel, a point would be 

 reached when a flood would cause the stream at some point in its course to overflow its banks, 

 and seek a new course through the low rolling hills, 

 after the flood had passed away, and then, in the new channel, the same process would be repeated ; 

 and this would occur again and again, while yet the general direction of the stream would remain 

 the same. It is easy to see how, in the constant repetition of this process, a stream in seeking a 

 new channel would often strike its old course again farther down, or even intersect and cross it, 

 running in some new direction. And thus it often happened that streams flowed in new direc- 

 tions over bodies of gravel previously accumulated, either by themselves or by some other streams. 

 The result of such an incident might be either a simple continued accumulation of gravel over the 

 same spot, but coming from a new direction, or it might be first the excavation of a new channel 

 to a greater or less depth through the previously gathered mass, and then, when this new channel 

 came to be filled again, it might be filled either with material perfectly similar to that through 

 which it had been excavated, or with something of entirely different character. 



This, it appears to me, is the general outline of the manner and means by which the ancient 

 auriferous gravel was slowly accumulated, its materials — that is, its gold as well as its boulders 

 and pebbles and sand — being derived from the bed-rock over which the streams ran, and from the 

 quartz, etc., which it contained. The longer such a process continued, the more the streams would 

 wander, the greater would be the quantity of gravel accumulated, and the greater the actual area 

 over which it would be spread. I think this process did continue until the advent of the volcanic 

 era, when the enormous quantities of volcanic matter, which were spread far and wide over the 

 western slope of the Sierra, buried beneath their mass the previously accumulated gravel, as well 

 as the rocks from which it was derived, and were, I think, the chief and direct cause of the final 

 ending of that gravel period. 



This new course the stream might retain 



Yet the process of the accumulation and distribution of tins volcanic matter, too, was slow, com- 

 plex, and long. The boulders of white lava occurring in the gravel near Placerville, beneath the 

 horizon of all the heavy accumulations of volcanic matter in that vicinity, and also the not infre- 

 quent intercalation of sheets of auriferous gravel between heavy masses of volcanic matter high 

 above the bed-rock, prove that in some sense the gravel period passed gradually into the volcanic, 

 and that there were long interruptions between successive deluges of volcanic matter, during which 







there was time for gravel to gather and spread over the earlier volcanic beds. The two periods 



