Doc. No. 9.J 37 



far beyond the line of travel to the east, of where this expedition left it, 

 it may extend, is equally as uncertain as was that portion of the ancient 

 sea-beach, and bottom, over which the United States exploring party 

 traveled the past season. The facts which have been gleaned from this 

 interesting region will appear in the forthcoming report of the expedi 

 tion, and from what little is now known of their operations, the parties 

 in charge of its several departments have manifested a determination of 

 purpose and assiduity in collating reliable testimony of this hitherto un 

 explored and unknown waste. 



Our present information of this remote section of the State, exhibits 

 in a still stronger light, the mutations to which the surface of the coun 

 try has been subjected, and which are probably persistent at the present 

 time ; to what period the changes of this district are particularly refera 

 ble will not be known probably until the following year, but enough has 

 already been developed which leads to the inference that the sea has 

 receded since the commencement of the tertiary era. 



VOLCANIC EOCKS PRECEDING- THE TERTIARY 



On a preceding page it was observed that a suite of rocks which are 

 often confounded with the recent volcanic group, existed in the Coast 

 Mountains, these rocks and their peculiar position will be noticed at the 

 present time. 



Following the west side of the Valley of Santa Clara, from the arroya 

 Francisquito in a southerly direction, a range of low hills, generally 

 barren in their appearance, is found, which protrude themselves into the 

 valley nearly at right angles to its course. The range of hills were ex 

 amined for the distance of forty miles, and in no instance, I believe, was 

 there a trace of any one of the sedimentary formations to be found upon 

 them. In this particular they differ much from the other volcanic series,, 

 either north or south of them, with the exception of those of the Santa 

 Anna range. 



Their naked and rugged aspect on the west side ' of these hills with 

 their peculiar local position leaves but little room for doubt, but that 

 they are the remains of the summit of ancient craters, elevated above 

 the surface of the then existing sea, prior to the deposition of the ma 

 rine formations which occur in other parts of the mountain range. 



This suite of rocks have evidently found their way to the surface 

 through the primitive rocks of this district, as it is found that they cut 

 the latter in several places in the form of dikes, while the debris of both 

 are found to enter largely into the components of the valley in which 

 they are situated. Another evidence, which lends confirmation to this 

 belief, is the fact, that had the emergence occurred at any time subse 

 quent to the tertiary era, we should have seen some traces of such a fact 

 in the elevation of those rocks of aqueous origin. The gradiency of the 

 entire northern portion of the valley Santa Clara will also be found in 

 commensurate with such an extensive series of disturbance as must have 

 occurred at the period when these hills were elevated above the surface. 

 The narrow limits within which thev are situated, would have - received 

 an inclination much greater than that which the surface now presents, 



