61 



operation of this kind is demonstrable only so far as may be legitimately inferred 

 from the natural position of the substratum as presented in their outcrop upon 

 the borders of such plains. We should have in view, at the same time, the 

 probable effect of those disruptive agencies which have elevated the edges on 

 either hand, and the law which governs those effects, when exerted over long 

 distances. In this country, as in every other which is similarly situated, the 

 smallest amount of inclination will be produced on originally horizontal strata 

 at the greatest distance from the immediate center of disturbance. On this 

 rule was founded the position assumed in my former report, in relation to this 

 subject, which is here referred to, together with a transverse section of the val 

 ley, in order the more fully to illustrate this portion of the present report. 



The superficial structure of the plain is now known to a depth of 400 feet 

 below the service, and if it be admitted that the rocks beneath the surface at 

 the center are in their proper position, which will be found to be the case, tak 

 ing the preceding rule as the basis of our calculations, we may thus be enabled 

 to make an approximation of the depth to the surface of the underlying rocks, 

 the superior of which is probably sandstone imposed upon a firm conglomerate 

 beneath them. 



It was stated in the report of last year, that a permanent supply of water 

 would not, in all probability, be obtained before the sandstone had been perfor 

 ated, unless, perchance, an arenaceous deposit should exist below the heavy upper 

 clay beds, and this underlaid by a deposit of plastic clays or argillaceous slates ; 

 in that case the depth of water would fall within 800 feet. 



I am not aware of any facts which would modify that opinion, and it is far 

 better for us to have the probable maximum before us rather than the minim am 

 of depth required, for, should we base our estimates of cost upon the latter, 

 there are strong probabilities that failure in obtaining water from these sources 

 would be the result even though a comparatively small depth might intervene 

 between the point of suspension and the point at which water might be found. 



An examination of the diagram exhibiting the transverse section of the basin 

 will develope the fact that the Stockton well is in all probability but little more 

 than half way down to the position assigned to the upper beds of sandstone, 

 and it is quite certain that if water is not obtained before reaching those rocks, 

 that it will be necessary to penetrate through their beds and obtain the supply 

 on the surface of the conglomerate. The only prospects of a permanent supply 

 of water being obtained at any depth less than twelve hundred feet, are the 

 probabilities which may exist of a deposit of sand being found immediately 

 below the beds which are now being bored, and this resting on an impervious 

 deposit as above mentioned. 



The following table of estimated depths under such a contingency as last pro 

 posed is given in order to direct attention to all of the favorable constructions 

 which may be adduced upon this interesting subject, and hoping that citizens 

 interested in it may be properly encouraged to persevere to the attainment of 

 successful practical results. The depths' in this table are estimated for a supply 

 of water above the sandstone, and at given distances east and west of the City 

 of Sacramento, and will be equally applicable to other localities upon these 

 plains, so far as they maintain nearly the same level above tide water. 



