

370 



R^SUMri AND THEORETICAL DISCUSSION. 



/ 





point. During that Survey, great efforts were made to obtain the necessary 

 information, and since that time, at a considerable number of points, more or 

 less systematic accounts have been kept, the chief results of which, so far as 

 the same have been accessible, are laid before the reader in the present 

 volume. From these data certain conclusions of value can be drawn ; while 

 in regard to other important points, we are left quite in the dark. 



It will be evident to all that there is little account to be made of any state- 

 ment of average value for the whole body of the high gravels. Neither is 

 the highest value an element of much importance : it may be taken for 

 granted that there are places, usually on or near the bed-rock surface, where 

 the gravel is immensely rich.* Tunnel claims of course give higher results 

 than the hydraulic mines do, because the former cannot be profitably worked, 

 except when the ground is rich. It is not at all uncommon for the bed-rock 

 surface to have been worked over by drifting, and the overlying gravel after- 

 wards w r ashed off by the hydraulic process.! 



The most desirable practical result to be obtained in regard to the hy- 

 draulic mining operations is an answer to the question, How low a tenor of 

 gravel can be profitably handled by this process ? Here a difficulty arises, for 

 the fact that a large amount of gravel has been worked, the average yield 

 of which has been low, is not a proof that the operation has been conducted 

 with profit or even without loss.J 



The following instances, however, of low rates of yield may be cited. At 

 Blue Tent, where the Company owns its own ditch, and consequently gets 

 its water at the lowest possible cost, a large quantity of top gravel was 

 hydraulicked, yielding 2.6 cents per cubic yard. The gravel was loose and 

 sandy, and easily moved. In this case the receipts " were barely sufficient 

 to cover expenses." This, perhaps, may be set down as being the poorest 



* The writer has seen $36 worth of gold panned out from as much dirt as could he conveniently carried away 

 in a lady's handkerchief ; the auriferous material was scraped from the bed-rock surface under a heavy deposit of 

 gravel. But Mr. Goodyear speaks of $1,100 in value having been obtained from a single pan of dirt. (See ante, 

 p. 117.) 



t While the gold, for reasons already given, is usually most concentrated on and near the surface of the bed- 

 rock, there are some exceptions to this rule ; and there are also occasionally very curious irregularities in the dis- 

 tribution of the precious metal : sometimes it is all in the upper layers of the gravel ; sometimes concentrated in 

 one or two pay-streaks, which may be very thin, while the intervening strata are entirely barren. But such 

 exceptional cases are, on the whole, quite rare. 



X Mining operations have been prosecuted, in repeated instances, for many years in succession, and on the 

 largest scale, involving an expenditure of millions, without any return whatever having been received. This state- 

 ment refers particularly to some of the mines on the Comstock Lode ; but what has been done there on a grand 

 scale may easily have been repeated elsewhere, although perhaps on a considerably smaller one. 



