134 GRAVEL AND PLACER MINING IN ALASKA. [bull. 263 
a pipe, multiply the number of cubic feet of water discharged pe 
minute by 144, and divide the product by the area of the pipe in 
square inches. The velocity in feet per second can then be found. 
Experiments by Mr. Hamilton Smith a appear to demonstrate that 
with new and carefully coated pipes, with velocit}^ as high as 11 feet 
per second, the loss of head is not significant. Nevertheless, the 
numerous conditions which enter into the laying of pipe lines on placer 
mines render the rule that the velocity should not exceed 3 feet per 
second in the pipe a very safe one to follow. It is a common fallacy 
among men inexperienced in hydraulicking that an increase in head 
will increase the amount of gravel which can be moved to the sluice. 
It must be remembered that the force of the water imparted by head 
is entirely expended in piping against the face, while the sluice is the 
governing factor in the moving of gravel after it leaves the face. The 
aid given by the water in moving gravel to the sluice, and in it is 
dependent on the grade over which it runs. In small hydraulic oper- 
ations water is conducted to the pit from the head ditch or penstock 
by means of canvas hose, known as flume hose, which is from 6 to 14; 
inches in diameter and weighs from S to 15 ounces per foot. This is 
used mainly on account of its cheapness and, as a less important con] 
sideration, because of the ease with which it may be moved about. 
It is used also for conveying water with very low head, for sluicing 
purposes. 
Flume hose is at best a makeshift and its use is not recommended, 
except in operations of primitive character in very remote districts. 
It should never be used to handle more than 100 inches of water or 
for a head greater than 50 feet. 
GIANTS AND NOZZLES. 
SIZES AND PRICES. 
The practice in using hydraulic discharge pipes, known as monitors, 
giants, and nozzles, does not differ in Alaska from that pursued else- 
where. 
Table 10 gives the principal facts necessary for the miner to know 
about hydraulic giants of the size most applicable for Alaskan work. 
"Smith, Hamilton, Hydraulics, 1XS6, p. 314. 
