PJBington.] DRIFT MINING. 97 
bank by menus of a small fireman's nozzle is the most successful method 
pphich has been so far tried to thaw ground under the above-mentioned 
jonditions. As regards the heating of the water, the system adopted 
it Fairbanks is to conduct the exhaust steam of the pump back into 
lie suction of the pump as it draws water from a sump alongside of it. 
rhis has been found more effective than simply turning the exhaust 
ripe directly into the sump itself. The water used is sometimes sup- 
plied in sufficient quantity from the mere seepage from the ice mixed 
vith the thawed gravel. But sometimes it will have to be introduced 
n the pit in small quantity. On the other hand, especially where 
hawed streaks occur naturally in the gravel, the water must be pumped 
>ut. This is done by the same pump used for the hydraulicking, with- 
>ut changing its position. 
This method of thawing by hot water piped against the bank has two 
advantages. The strongest appears to be the fact that gravel thawed 
)y this method can, as it were, be selected in the face, and no higher 
gravel than may be profitable need be taken down. The portion of 
he gravel above the part taken down remains solidly frozen, and con- 
equently the roof of the drift or wide stope does not cave any worse 
han does the roof of solid muck in drifting operations where all the 
gravel in its complete vertical section is extracted. Another advan- 
age is that the gravel is moved from its original position farther than 
)y steam, and if it contains clay the clay has less opportunity to bake 
.nd cake than with steam thawing, and the amount of hand work in 
ricking down the gravel is lessened. 
A serious objection to thawing by hot water may justifiably be raised 
n cases where the bed rock consists of large slabs of schist, into which 
he gold sinks from 1 to 4 feet and even more. In such a case the 
yater can not be piped to reach all the frozen gold-bearing material. 
Although I am not aware that a combination of the hot-water and 
iteam-thawing methods has been tried in such a case as the above, it 
eems not impossible that such a combination would be the most eco- 
lomical. On the other hand, where the bed rock consists of finely 
pmminuted schist or softened, thoroughly rotten rock, even should the 
[old be found in it to the depth of 2 feet, there can be no valid objec- 
on to the hot-water hydraulicking method. In the Nome district 
f Seward Peninsula, where the hot- water method was tried, it was 
und that the water finally became too thick with sediment to be used 
the pump, and the system was abandoned. 
A minor recommendation for the use of the hot-water method is the 
ct that all the unpleasantness of the steam method, which fills the 
orkings with steam, creates dampness, etc., is obviated, and the walls 
id roof of the drifts are dry, while ditches cut in the bed rock on 
rade to the pump sump can be so cut as to prevent the floors from 
Bull. 263—05 7 
