114 
GRAVEL AND PLACER MINING IN ALASKA. 
[bull. \ 
The apparent extraordinary fall of the Tread well ditch (over 20 ft 
to the mile) may be accounted for by the fact that it has, at each ere 
which it taps in its course, a drop off of 6 to 7 feet, and reservoir, 
which are relief gates, as illustrated in the photograph of the ditch 
Lawson Creek. (See PL XVI, B.) One of the waste gates sho^ 
on PI. XVI, B, is 5 feet 4 inches wide; the other is 6 feet 7 inct 
wide and 3 feet 3 inches deep. There is a smaller auxiliary gs 
4 feet 6 inches wide and 2 feet deep. 
The Treadwell main ditch is 14 miles in length, and is supplement 
by 4 miles of subsidiary ditches/' The main ditch heads in Fi 
Creek, and its supply of water is obtained successively from Eag 
Cowee, Lawson, and Paris creeks, while an additional ditch brings wat 
Fig. 19.— Map of portion of Juneau district. 
IS US 
from Ready Bullion and Bullion creeks. In summer the water 
for running 760 of the 880 stamps of the mills, but in winter it is r 
used for power purposes. 6 
The main ditch has a width of 7 feet on top and 6 feet on the b< 
torn, and a depth of 5 feet. In 1904 construction was going on 
portions of the ditch line as follows: Twelve-inch posts, in sets wi* 
5-foot centers, were being placed along the inside of the ditch, leavi 
space 5 feet in the clear at bottom and 4^ feet in the clear at top, wi* 
7-inch cap logs 4J feet between shoulders. Lagging split 3 inct 
thick and 1£ feet wide was laid inside the posts. Moss and sod w€ 
"See Kinzie, R. A , The Treadwell group of mines, Douglas Island, Alaska: Trans. Am. Inst. IV: 
Eng., vol. 34, 1901, p. 374. 
''It is to be regretted that full data regarding the Treadwell ditch are not at hand. 
