58 



unknown, and there is as yet no method of reasoning upon its probable depth from 

 any data in our possession which would amount to more than mere speculation. 

 There is no evidence respecting it beyond twenty or thirty feet, which is all that 

 has thus far been known. 



This deposit has all the appearance of having been originally covered by the 

 waters of the ocean, as small fragments of what appear to be marine shells have 

 been met with at different points, though none of them in a state of sufficient pres 

 ervation to enable us to determine either the genera or species to which they belong. 

 Should this prove to be the equivalent of the Santa Clara deposit, its average 

 thickness might be put down at about one hundred feet, or if like the Los Angeles 

 bed, then the boring of four hundred and thirty-five feet has not yet penetrated 

 through it. There are reasons for the supposition that this blue clay is not less 

 than that of the valley of Santa Clara, and the likelihood of its being much thicker 

 is admissible. We think two hundred feet might be set down as a reasonable sup 

 position respecting its depth, which, should it prove correct, will present the proba 

 bilities of obtaining water from beneath it, at a distance of fifteen miles from Sac 

 ramento City, about at the same depth at which we estimated it last year, the 

 difference between the estimate of last year and the present, being only forty-five 

 feet, and both estimates being made without any reference to each other. In the 

 northern part of the valley, the heavy deposit of clay which has been mentioned as 

 resting on the slates, so far as opportunity offered for examining it, seemed but little 

 disturbed, and from its general appearance, I was subsequently led to the belief 

 that it was the same as that found on the surface of the lower bottoms further south. 

 But I am unable to speak with much certainty upon that point, as no organic 

 remains were observed by which its identity could be satisfactorily proved. The 

 presumption upon this subject, that it is identical, is based on the very tenacious 

 character which it possessed, and its peculiarity of color, two features noticeable 

 only in these lower beds on the southern levels of the plain. 



Should this bed ultimately prove to be identical with those forming the surface 

 of the lower bottoms, for which result we have good grounds of supposition, then its 

 thickness as indicated by its outcrop in the upper part of the valley cannot be less 

 than we have herein estimated it, and would fix the bottom of that deposit at the 

 depth of a little more than seven hundred feet. Short of this water will not proba 

 bly be found in that of the country in any permanent supply. 



The depth of seven hundred feet for an artesian well is not excessive, and may 

 be esteemed even small, when we consider to what depths this description of wells 

 have been carried in other parts of the United States and Europe. A failure to 

 obtain water at this depth should not discourage the enterprise, for the structure of 

 this basin, in every part of it, is such as to warrant a certainty of obtaining water 

 beneath its surface if the operation of boring is carried to the extent which the 

 geological conformation of the ground requires. The case of the artesian well in 

 North Carolina which has been completed within the past year, furnishes a good 

 illustration of the depth to which it may, at times, be necessary to descend to obtain 

 a permanent supply of water. This well has been completed at a depth of 2700 

 feet, and a copious supply obtained. This fact alone should be an incentive to perse 

 verance in the prosecution of such enterprises beyond any depth to which they 

 have yet reached in our State. 



A great uniformity appears "in the disposition of the earthy deposits forming the 

 superstructure of the San Joaquin and Sacramento valleys, above the rocks at their 

 base. The interesting suite of specimens from the artesian boring at Stockton, 

 sent by Mr. George E. Drew to the Academy of Natural Science at San Francisco, 

 with an accompanying paper giving the depth of each of the beds, and their respect 

 ive distances below the surface, assists us much, with other collateral evidences in 

 forming an opinion of the relative positions of the bedg below and those above the 



