?urington.] DRIFT MINING. 95 
the seven-eighths inch cable, the hook to which is attached the bucket 
occupies the position indicated by the solid line. The cam, A, lies 
horizontally and is held firmly in this position by the dog, B, the 
weight of the bucket pressing the notch of the cam against the point 
;>f the dog, f. When the carrier reaches the head of the shaft the 
3nd, c, of the dog strikes the block, D, and frees the point of the dog 
from the notch of the cam. The front of the cam now occupies the 
position indicated by the dotted line, and, as the bucket sinks into the 
shaft, is pressed against the block, since the carrier tends to move 
backward. Thus as the bucket sinks with the hook on the one-half 
inch cable the carrier is held firm. 
As the bucket rises from the shaft or pit, the strain is toward the 
sngine, and the lower end of the dog, e, still prevents the apparatus 
from moving. 
When, however, the cam, A, by the upward movement of the 
bucket, reaches the horizontal position indicated by the solid lines, 
the point of the dog, y, jumps into the notch, lowering at the same 
time the point, e, which allows the carrier to move up the seven- 
gighths inch conveying cable, and also once more secures the cam in 
its horizontal position. 
The block attached to the cable is held in a vertical position by a 
suspended log or block, which insures its engaging with the dog. 
By this system of working, if the self-dumping rig handles 250 of 
the 30-pan buckets in ten hours or, roughly, 60 cubic yards, the plant 
will necessitate the employment of 12 men, namely, 2 firemen, 1 hoist 
man, 1 point man, and 6 men shoveling and wheeling, beside the fore- 
man. The ordinary set-up of the self-dumper is shown in fig. 13. 
The boiler used for generating the steam for points at night is used 
for running the hoist in the daytime. In running from 15 to 20 
points at night it will burn a cord of wood, and. in hoisting in the 
daytime will burn from one-half to 1 cord more. The total daily 
twenty-four-hour expense can not be brought below $130 and will 
probably amount to $150. It is evident that with such a plant the 
enor of the gravel must amount to at least $2.60 to the cubic yard to 
ay any profit at all, exclusive of washing in the spring, and should 
e 4 cents to the pan, or $5.20 to the yard, to pay a profit which cond- 
ensates for operating in so remote and expensive a country. The 
ost of washing in the spring is in general from 50 cents to %\ per 
iubic yard. 
The winter dumps are piled in a conical heap around the gin pole, 
:o which the trolley cable of the self-dumper has been attached while 
pie dumping is in progress. In laying out the space for the dump, 
he string of boxes in which the gravel is to he washed during the 
ollowing spring is so laid that it will bisect the proposed cone, having 
ts proper grade and length. When the spring opens the dump is 
