9 76 



RESUME AND THEORETICAL DISCUSSION. 



auriferous, deposit is already almost entirely worked out ; in others, the top 

 gravel has been washed away, leaving the lower beds, which may be much 

 richer than the upper ones, and, at the same time, more difficult of attack. 

 Again, there are regions where a vast amount of gravel remains untouched, 

 on account of the heavy capping of volcanic materials, either too hard to be 

 hydraulicked, or too thick to be washed away with profit. In other districts 

 there is still much gravel of low tenor to be washed, whenever the capital is 

 forthcoming to supply water at a sufficiently low price. Again, there are 

 apparently magnificent fields for enterprise, ready to hand, in laying open 

 as yet almost untouched deposits, where the chief obstacle to development 

 has hitherto been the difficulty of consolidating claims, by purchase or other- 

 wise, without very large expenditures. 



On the whole, it is evident from a consideration of the facts laid before the 

 public in the present volume, that the hydraulic mining business may still 

 be successfully prosecuted through many years before the field is exhausted. 

 And it is probable that for quite a number of years to come the product of 

 gold will not be materially diminished. The most serious obstacle likely to be 

 met with is the filling of the valleys with tailings, thus hindering washing, and 

 also exciting alarm and opposition on the part of the agricultural population 

 of the belt of land adjacent to the foot-hills. Here complications may arise, 

 putting a less favorable aspect on the hydraulic mining interest. Indeed, 

 the possible condition of the western slope of the Sierra after the streams 

 have become choked with tailings, the gold mines exhausted, and the prin- 

 cipal part of the timber cut down, is not one satisfactory to contemplate. 

 There is no part of the world where scientific oversight and judicious legis- 

 lative interference is more desirable for the future welfare of the community 

 than in the Sierra Nevada of California. 



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