79 
n the Treadwell workings, but even here there are great variations 
in the gold tenor at different places. On the 110-foot level all the 
rock was minable; on the 220-foot level from 10 to 40 feet of low-grade 
stuff was left on the foot, excepting for a distance of about 150 feet. 
3n the 330-foot level good values were found up to the slate, except- 
ng for 200 feet along the west end, where 20 feet or so were left, while 
)n the 410-foot level not over half of the rock gave assays over $1. 
PERSISTENCE IN DEPTH. 
The ore dikes have been developed along the dip for a distance of 
ipproximately 1,000 feet in all three of the mines now operated. 
Che Treadwell workings reach about 700 feet below sea level, the 
Mexican 600 feet, and the Ready Bullion 800 feet/* In no case has it 
)een possible to make out any progressive change in the character of 
;he ore as depth was attained. The assay charts show the ore in the 
owest levels to be as good as in the upper workings, and it is evident 
;hat variations along the dip are not greater than those observed from 
)lace to place along the strike. It is true that the mine records for a 
Deriod of years show a gradual decrease in the per- ton value of the 
naterial which has been treated. This is especially noticeable in 
he case of the Treadwell mine, which has been the longest in opera- 
ion, but it is the result of increasing the tonnage by mining low-grade 
ock rather than an indication that the average value is decreasing 
v r ith depth. 
It seems fair to assume that the ore will continue to at least a con- 
iderably greater depth without important change in average value. 
?here is nothing in the character of the ore to indicate any important 
econdary concentration of values by oxidizing waters near the sur- 
ace. On the other hand, the characteristics of the deposit are 
>elieved to indicate that it was formed in its present condition by the 
irect action of ascending waters. If this idea is correct, there can 
>e little doubt that the mineralization and the values will continue to 
much greater depth than has been reached, and it may be reasonably 
xpected that the limit of deep mining will finally depend more upon 
ncreasing costs of hoisting and pumping than upon the exhaustion of 
he ore. 
VEINING IN THE ORE BODIES. 
In almost all parts of the Treadwell deposit reticulating veinlets 
f calcite and quartz are prominent features of the mineralized 
ikes. The veinlets are often composed entirely of calcite, but 
his mineral is usually accompanied by quartz, though the latter sel- 
om, if ever, occurs by itself. The veinlets are rarely more than a 
ew inches in width; many are only a fraction of an inch across, and 
a October, 1903. 
