. THE COMSTOCK LODE. 71 



more intermingled with these minute fragments of propylite, until they finally 

 occupy the entire zone, and in their turn give place to the clays. 



Clays. — The clays, so constant an accompaniment of all lines of dislocation 

 throughout the lode, are formed, as will hereafter be seen^ from the decom- 

 position of propylite rock. Those clays, lying upon the syenite front of Mount 

 Davidson, are far more the result of propylite decomposition than of the sye- 

 nite. Syenite itself produces but little clay; and wherever a sheet lies 

 between two masses of that rock it is of extreme thinness, and of a dark, 

 earthy nature, possessing none of the remarkable chemical and physical prop- 

 erties of the other Comstock clay. Lying along the entire east wall is a con- 

 tinuous sheet of at least 20,000 feet in length; the average thickness may be 

 safely estimated at two feet. Wherever the wall presents to the west a very 

 sharp conchoidal curve, and, in general, wherever abrupt turns are made, the 

 clay thickens to a great extent. Such notable examples as that in the Con- 

 solidated shaft, the Empire section, the point, shown on Atlas-Plate 11, on the 

 east wall of the Savage, and the breadth described in the Palmer shaft of the 

 Ophir, are its extremes of thickness; but many places occur where it attains 

 a width of eight and ten feet. The interior structures of these thick, pasty 

 bodies vary curiously with their position; those which accompany sharp turns 

 are ordinarily subdivided into flakes, while the straighter sheets are cleavable 

 into parallel plates. The characteristic of the east clay is the pebbles of 

 smoothly-rolled quartz which it contains. No one of these pebbles, so far as 

 examined, and observations have been made from the Ophir to the Crown 

 Point, ever contains a particle of silver. The west clay, equally continuous 

 with the east, is less dense, thinner, never charged with rolled pebbles, and 

 lacks the remarkable property of expansion which the east and interior clays 

 possess. 



Whoever undertakes to study the interior systems of clay sheets which 

 intersect the horse materials, will find that their continuity is almost impossi- 

 ble to trace out. After continuing in a given direction for several hundred 

 feet, they will break sharply oflT at an angle and fault to the right or left, losing 

 themselves in interminable zigzags through the horses. There is no unravel- 

 ing the relation of this network of veins; and upon the diagrams the writer 

 has been careful to have recorded only those sheets whose continuity has been 

 identified beyond a doubt. 



