THE LODE. 287 



from time to time, and so may the quantity of active reagents in the rising 

 Avaters. On the whole, the earlier deposits of quartz seem to have been of 

 lower grade than the later ones, but the phenomena are so complicated that 

 no considerable practical value attaches to this observation. 



The ore was deposited on the walls and fragments of rock as in more 

 regular veins, but the currents percolating from the east and decomposing 

 the rock through which they passed, gave the east wall a somewhat indefi- 

 nite character. This indefiniteness was increased by the dynamical action 

 which followed the deposition of quartz, and probably also accompanied it. 

 After most of the quartz was precipitated, renewed movements occurred, 

 crushing the deposits in great part to so-called " sugar quartz." It was the 

 quartz bodies standing at a considerable angle to the west wall, and there- 

 fore crossing the fissure planes, which were most extensively comminuted. 

 More attrition products were of course also formed at the same time. 



The solutions which so powerfully attacked the polyhedral fragments 

 of diabase were of course not without efi"ect on the pulverized rock masses 

 which were abundant, particularly in and near the secondary fracture, 

 or " east vein." The clays are the result. In a simple vein, attrition mix- 

 tures and clays are apt to occur only on the two walls. On the Comstock 

 such a regular formation is found on the west wall, but seldom on the east. 

 There is no necessary connection between walls and clays in spite of their 

 frequent association, some typical veins showing nothing of the kind. The 

 clays of the Comstock show little kaolin. 



Probabilities. — The first condition for a deposit of ore is the formation of 

 an opening, and on the Comstock such spaces appear to have formed in 

 three distinct ways, already explained. The secondary fracture has been 

 worked out, and except in Gold Hill considerable nonconformity of the walls 

 is not to be looked for. There it is as likely to occur at greater depths as 

 above ; indeed, the fact of its occurrence in the Croicn Point and Belcher, at 

 a mean depth of, say, 1,700 feet from the Gould (£ Curry croppings, leads 

 almost necessarily to the conclusion that there must be other nonconformi- 

 ties at greater depths, unless the rocks change to other species. Openings 

 of the type of that which contained the Consolidated Virginia and California 

 bonanza may occur at any point on the vein, and wholly without warning 



