66 



during this portion of the tertiary era a submarine deposit of drift was formed and 

 that subsequently the superior conglomerates had their origin, and are now found 

 superimposed upon the deposits above named. Should this doctrine be finally 

 demonstrated by more extensive and well directed improvements in mining opera 

 tions, and the facts before us at the present moment most certainly favor the pre 

 sumption that it is probably correct, than a new and wider field for mining opera 

 tions is soon to open in this district of the State, and we may reasonably expect to 

 meet with deposits equally valuable beneath these rocks in other parts of the State, 

 on the same line of elevation, as those which have already been developed in the 

 counties of Placer and Sacramento. 



In this State it is well known that numerous instances have occurred in the min 

 ing districts where the miners have passed through the sedimentary rocks, (slates,) 

 and found the deposits of gravel drift beneath, the same containing gold in fully 

 equal quantities with that found in the surface material above them, and which was 

 thought the foundation stone below which no gold would be found. These 

 suggestions are not made as bringing to light any new principle in relation to placer 

 deposits, for facts of similar character have been known for three years past in different 

 sections of the State. The present case relating to the placer deposits of the coun 

 ties of Sacramento and Placer, may be regarded as corroborative testimony of our 

 former knowledge, and the existence of a much more extensive range of this char 

 acter, than has heretofore been discovered. 



The position of these auriferous deposits in the counties above named, and the 

 corresponding character of a large portion of country lying north and south of the 

 above section is adverted to at the present moment for the purpose of directing at 

 tention to those districts near the foot-hills which present similar features, and which 

 are as yet untouched. These districts on either hand having the same altitude 

 above the plains present equal certainties of the existence of the same deposits as 

 those met with in the county of Placer. Under the head of placer mining, I shall 

 have occasion to allnde to this subject again. 



The other members of the tertiary group on the foot-hills of the Sierra Nevada, 

 consists of sandstones and clays, the most important of which are found upon the 

 Cosumnes and other rivers south of this stream. The sandstone beds as far as ex 

 amined have every appearance of being much more recent than any member of the 

 stratified rocks of which we have heretofore spoken, and their position is evidently 

 tinconformable with the latter, resting very evidently on rocks having a much high 

 er degree of inclination. In fav< ;rable localities for their examination, I have found 

 their depth to exceed 110 feet. An instance of this kind is afforded upon the 

 banks of the Tuolumne River, at a distance of two miles east of Jackson's Ferry. 



As a general rule, these rocks have been but little, if any, disturbed, having 

 but a slight inclination from the horizontal, and it might be said none, except 

 that which is found to correspond with the gradiency of the plains beyond, and 

 seldom exceeding two or three degrees. Immediately east of these deposits, 

 and as you enter the hills, the other sedimentary rocks are seen cropping out 

 and assuming high angles of inclination which are found to increase as you 

 travel in an easterly direction. 



Sufficient opportunity did not offer for a more critical examination of the re 

 cent sandstones than that of a mere passing notice. It would be desirable that 

 they should receive a closer investigation during the coming season, than was 

 afforded, from want of time during the past summer. Their proper place in the 

 tertiary formations must be deferred until that time shall arrive, when we shall 

 be able to speak with more precision in relation to the peculiarities which they 

 may present. The older tertiaries in the more elevated portions of the moun 

 tains are more or less auriferous in n'early every locality in which they have been 

 examined. 



The soft clays which are at times found between the slates and conglomerates, 



