pjBiNGTON.] DRIFT MTNING, 91 
>ient method in general practice for thawing frozen gravel. The 
imount of moisture contained in steam can be judged by the color of 
l jet of steam issuing from a small brass pet cock. If it is trans- 
ient or whitish near the orifice it contains less than 2 per cent of 
noisture; if pure white, the moisture is above 2 per cent. 
Fig. 17 shows the details of the steam point and some of the fittings 
vhich its use entails. 
In creek claims exceeding 15 feet in depth where solidly frozen 
ground occurs, as, for example, in the new Fairbanks district of 
Llaska, the method of drifting with the use of the steam point is as fol- 
ows: A 20-horsepower boiler, capable of running 10 steam points, is put 
>n the ground, and frequently one or two extra long points are provided 
or sinking holes. These long points, from 10 to 12 feet in length, are 
ot so strongly made as the 5-foot points used in the drifting opera- 
ions. In some cases pieces of one-half-inch hydraulic pipe are used, 
'he point is set up on the ground and steam or hot water is turned 
n. The time for sinking a hole by this method to bed rock is from 
wenty-four to forty-eight hours. If large, flat stones are encoun- 
Bred in the gravel underlying the muck it is sometimes advisable to 
se strong, specially made points to prevent breaking. The average 
adius of a vertical shaft thus thawed by a single point is 2 feet, and 
le hole when cleaned out has a cylindrical or tube shape. 
If timbering is required after the shaft is sunk it is generally found 
sat the hole will thaw sufficiently to allow the shaft to be carried 4 by 
feet or 4 by 6 feet inside the timbers. As a rule, however, winter 
hafts are not timbered. When bed rock is reached a tunnel or run- 
ray is run for a distance varying from 50 to 100 feet from the tunnel 
ingthwise of the claim. From this central drift, which is generally 
[inhered, lateral drifts are run to a distance not exceeding 50 feet, or 
rom this down to 10 feet, or the width of the pay streak. Two tun- 
els parallel with the central runway are carried at the ends of the 
ross drifts and connections made from them to the shaft. These are 
a rely timbered. 
The frozen condition of the overburden allows a firm roof to stand 
r ithout timbering while the gravel is being extracted. This is a great 
d vantage and in part offsets the difficulties attending the breaking 
p of the frozen gravel. The ground is now ready for working. The 
rifts and main ways are run as low as possible in cases where the ip&y 
i thin, but a height of 3^ feet is the lowest that can be worked with 
conomy. 
During the night shift sufficient gravel is thawed to occupy the 
len in extracting it in the daytime. In handling, not only the pick- 
lg and shoveling from the bank must be allowed for, but the wheeling 
) the shaft, the time of return to the face, and the hoisting of the 
