CHAPTER XXVII. 219 



They became farther separated by shifting from one side to the other 

 of the great valley in different ages, just as we see them doing today. 

 The consequence ''s a vast number of different gravel channels of dif- 

 'erent sizes, depths and distances from each other. 



Most of these are probably still connected with the original source 

 of supply by a thread of gravel or sand, while some have a well defined 

 channel directly connected with the water that sinks at the foot of th: 

 mountains today. While it is impossible to say how large any of these 

 arc or how much water they contain, it is certain that their number 

 is very large. The area through which they have swung is so great 

 and the period so immense that it cannot be otherwise. It is reason- 

 able to suppose that the older ones formed when the mountains were 

 highest and the wash into the valleys was the coarsest now carry the 

 most water today, although most of them must be out of reach of all 

 ordinary well boring. 



In the course of time and probably long after the valleys began to 

 fill, the country sank and a part became lower than the sea. Then 

 came in a vast wash from the west or north, or both, perhaps from 

 the melting of the great northern glaciers. This brought in vast banks 

 of gravel, sand and clay and other deposits far more recent than the 

 granits of the interior hills. In San Diego county this formed a mesa 

 some fifty miles long, ten mile wide and nearly five hundred feet high, 

 lying along the coast. How deep it is no one knows, but in the Sweet- 

 water Valley, five hundred feet below the highest levels of the mesa, 

 a well was bored eleven hundred feet without going through it. This 

 would make it over sixteen hundred feet thick at that point. In 

 Orange county this formed the hills of shale that lie along the lower 

 coast, which have since decayed upon the top into adobe. Its oldest 

 form is probably in the conglomerate that lies across the mouth of 

 Santiago Canyon, running many miles up the canyon, and reaching 

 some distance on each side of it. Back of Whlttier and Fullerton this 

 runs into hills of shale again, and these continue on to Los Angeles, 

 running on the west and south into gravel, sand and clay deposits, but 

 all of the same general formation. On the northwest and west they 

 run into the granite of the Cahuenga hills, and these again into con- 

 glomerate of an older date in the Santa Monica mountains, changing 

 into an older conglomerate in Ventura, and from there continuing along 

 the coast of Santa Barbara. 



Nowhere east of its course is there any track of its path showing 



