ptjrington.] WATER SUPPLY. 43 
assumes a somewhat steeper angle than that of loose material. One 
measured in the Klondike had a slope of 40°. From experience it has 
been found that if the ground is of uniform richness, 80 per cent of 
the values are contained in the upper two-thirds of the dump, which 
has a content of approximately 8,000 cubic yards. The apex of the 
dumps is generally 30 to 40 feet above the base. Four times each day 
5 pans are taken in sampling — one from each quadrant of the clump 
one-half way down from the top — and one pan from the apex. The 
results of the 20 pannings are put together before weighing, and 50 
per cent of the result is taken for the average value of what has been 
taken out during the day. 
Neglect to appty some form of sampling to the dumps has caused 
manv lamentable failures in the Klondike. Winter operators of the 
Fairbanks district should keep themselves assured by constant sam- 
pling that the gravel they are getting out at such a cost carries values. 
WATER SUPPLY. 
CLIMATIC CONDITIONS. 
Land areas in high northern latitudes are characterized by distribu- 
tion of their natural resources that is unfavorable to economic use. 
In Alaska the great forests that characterize the south coast are 
replaced by stunted growths of spruce in the gold fields of the interior 
and by willow copses in Seward Peninsula. During a normal year the 
rainfall at Juneau, as may be seen from table 2 (p. 48) compiled by 
Dr. Cleveland Abbe, jr., is over eight times as great as at Eagle, 
on Yukon River. The catchment area at Juneau is only 4 square 
miles, and, as the grades of the hillsides are precipitous, the rainfall 
quickly runs off. A small amount of the water is used for power in 
connection with milling operations and for mining placer gold. The 
lort, steep creeks and rivers of the south coast have small catchment 
Dasins, and even were there any use for the water for placer-mining 
purposes, there would be difficulty in impounding it after the melting 
)f the snows in June and July. 
Large catchment basins exist in the interior of Alaska, but the water 
o fill them is unfortunately lacking. At Eagle, where the annual 
■ainfall is 11.4 inches in a normal year, the drainage area of Mission 
reek and its tributaries which flow into the Yukon is nearly 200 square 
ailes. Of the amount of water caught in a given area, however, very 
ttle is available for mining purposes. As an illustration take the 
ase of American Creek, a tributary of Mission Creek. The only 
lacer mining on it is done at a point about 12 miles distant from its 
louth, atan elevation of 1,600 feet. As the use of water for hydraulic 
lining requires a head of 200 feet, and as the height of the divides 
hich surround American Creek does not exceed 3,000 feet, it is evi- 
ent that the only catchment area available is that lying between 1,800 
