purington.] HYDRAULIC MINING. 151 
In California hydraulic mines the dump, even after a scries of drop- 
offs 25 feet in height, was sometimes in a canyon hundreds of feel 
vertically below the end of the sluice. The remarkable topographic 
conditions which allowed of such a phenomenal dump probably can not 
be found in another placer country, and certainly not in those portions 
of Alaska here considered. Even in California, however, it was often 
found necessary to distribute the dump by means of Y\s near the end 
of the tail sluice. One such system is in practice on McKee Creek, 
Atlin, and has already been referred to. In hydraulic operations 
where 1,000 cubic yards or more a day are handled with low dump 
two carpenters have frequently to be employed at least half of the 
time in adding boxes to the tail sluice. If the dump be properly 
spread in delta form, the operation can be carried on in places where 
otherwise it might be impossible. 
Where hydraulic operations are conducted in creek beds of low 
grade, below the so-called "sluice-box grade," or 6 inches in 12 feet, 
some expedient must be adopted to get rid of the accumulation of 
tailings below the end of the sluice. If the topography is such that 
the water runs off and only the solid residue of the tailings accumu- 
lates, the expedient is sometimes adopted of "piping" the dump away 
with an extra giant set in a convenient position for the work. This 
giant generally requires the services of one man, and, although used 
only a portion of the time, may be figured under Alaska conditions 
to add from 2 to 5 cents to the cost of handling the gravel. The effi- 
ciency of the plant is detracted from by so much power as is 
required to push the tailings out of the wa}^. It can not be too strongly 
insisted on that when this or any other device is used to move or ele- 
vate the tailings, the strict principle of hydraulic mining is departed 
from. The use of the steam or horse scraper in removing the tailings 
of small plants is discussed on pages 70-72. 
If the grade of the creek bed is lower than that necessary for the 
sluice, the tailings must be elevated and the water pumped from the 
pit. Mechanical elevators with the addition of a bed-rock drain are 
sometimes used, though not with success, so far as known. In one 
case on Mastodon Creek of the Birch Creek district the installation of 
a steam scraper for lifting the tailings from the hydraulic pit was con- 
templated, the water being bandied by a bed-rock drain, which had 
been installed at great expense. 
THE HYDRAULIC ELEVATOR. 
The hydraulic elevator is too well known to need elaborate descrip- 
tion. The principle is the same as that of the injector. Water under 
pressure discharged through a nozzle set w it hi n a steel jacket creates 
a vacuum and causes Avater — about one-half the quantity used by the 
elevator — and accompanying solid material to rise to a height corre- 
