150 ALASKAN MINERAL RESOURCES IN 1906. 
quartzite bowlders, reaching 18 inches in diameter, in a layer of muck 
and decomposed vegetable matter lying above the gravels. The 
granite is but slightly decomposed and the bowlders are rather angular. 
These facts suggest a different transporting agent than running water. 
Associated with the auriferous gravels are in many places thin strata 
of cemented gravels in which the cementing material is mainly calcite. 
The cemented character prevents the separation of the gold in the< 
sluice boxes, so that if much of this sort of gravel should be encoun- 
tered recourse to some method of crushing would be necessary. 
On Melsing Creek a method of preparing the sluice boxes which has 
not been seen in any other part of the peninsula was noted. This 
consisted of nailing a strip of canvas or cocoa matting on a plank 
slightly narrower than the bottom of the sluice box. On top of the 
canvas a strip of galvanized-iron screen, with about one-fourth inch 
mesh and the same width as the plank, was fastened. In use, this 
plank was placed in the bottom of the sluice box and the riffles laid 
on top, thus holding it in position. To clean, the plank was taken 
out of the sluice box, turned upside down, and pounded with a ham- 
mer or mallet. Although no comparative figures were available tc 
prove the added efficiency of the sluice boxes thus equipped, the 
operator was completely satisfied with the results, as he was con-i 
vinced that the additional saving of gold was very great. It is ol 
course not necessary that every box in a set should be equipped withl 
such a false bottom. Individual practice and study will determine 
the most effective number for different kinds of gold. 
OPHIR CREEK. 
Ophir Creek still continues to be the most productive of the tribu- 
taries of the Niukluk. The development of the placer claims along 
its course and on its main tributaries — such as Dutch, Crooked, and 
Sweetcake creeks — has constantly demanded additional water supply 
with greater head. To meet this demand high-level ditches have 
been constructed, but it was early recognized that even under thd 
most favorable circumstances Ophir Creek could not be relied on tc 
meet the growing demands. Consequently it has been necessary tc 
lead water from other drainage areas into the Ophir Creek basin 
The largest operation of this kind has been successfully carried out 
and undoubtedly permitted mining which the dry weather of lasl 
summer would have otherwise prohibited. This ditch takes watei 
from Pargon River at Helen Creek, a small tributary about 2 miles 
north of the summit of Mount Chauik. The ditch is 11 miles long 
and in many places, where the slopes are excessive, flumes have beer 
constructed. The water is led around the eastern flank of Mounl 
Chauik and thence across the divide into the Ophir Creek basin. Ir 
order to obviate additional ditch construction, the water is discharged 
