Ch. VI.] QUARTZ LODES. 91 



perhaps, originated the belief that auriferous lodes 

 deteriorate in value in depth. I at one time, after 

 having studied the auriferous quartz veins of Australia, 

 advocated this theory which was first insisted upon by 

 Sir R. I. Murchison, but further experience in North 

 Wales, Nova Scotia, Brazil, and Central America, has 

 led me to doubt its correctness, excepting in cases such 

 as we have been considering, where there has been an 

 accumulation of gold in the superficial portions of lode?, 

 since their original formation. Gold is distributed in 

 quartz veins in bands, and patches of richer stone of 

 more or less extent. These richer portions of the lodes, 

 if sunk upon perpendicularly, will be passed through, 

 but so also they would be if followed horizontally, their 

 extent in one direction being as great as it is in the 

 other. The chances of meeting with further patches of 

 rich ore in depth, after one has been passed through, 

 are about the same as they are in driving horizontally, 

 and the frequency therefore with which the auriferous 

 ores are met with along the surface will, as a rule, be an 

 index of their occurrence in depth, if we be careful in 

 distinguishing deposits belonging to the original condi- 

 tion of the lodes, and those due to subsequent con- 

 centration. To do this we must get below the imme- 

 diate surface, and take as our guide the gold occurring 

 in the solid undecomposed quartz, and not the loose 

 grains contained in the fissures and cavities. 



The lodes of Santo Domingo are worked by means of 

 levels driven from near the bottoms of the valleys that 

 intersect them. When these levels have entered suffi- 

 ciently far into the hills, shafts are driven upwards from 

 them to the surface, and other levels driven sixtv feet 



