376 The American Geologist. June, 1892 
the origin of this gulch it may have been produced by glacial 
action or by the denudation of running waters from freshets and 
melted snows. The richest localities in this gulch were the outer 
points and margins of the slopes at the termini of the finger-like 
streams. This is easily explained also by the deposition of the 
coarser gold at the head of the gulch. If the gold continues to 
stream down and follow chosen finger-like paths, in the vicinity of 
the veins in such a placer, the denudation presumably being slow, 
the occurrence of nuggets of such an unusual size as 20 ounces 
might be explained on the theory that persulphate of iron holding 
an appreciable amount of gold in solution deposited its gold in a 
certain spot, a large mass of gold thus gradually accruing. This 
-_ 
theory is given in Le Conte’s text book of geology, in reference 
to the auriferous gravels of California. 
As illustrating No. 3, in the Flint Creek valley in western Mon- 
tana, Deer Lodge county, near Stone, placer beds occur in the 
form of long bars or level plateaus which extend for several miles 
north from the mountain ranges. They terminate abruptly in a 
cliff-like margin. 
The gold bed A, Fig. 2, occupies the upper stratum of this plateau 
for several feet, and is sharply marked off from the lower gravels 
B. The gold stratum was evidently a later flow from the mount- 
ain, and has: been rearranged and deposited by lake action. 
These plateaus have been the result of glacial action in this in- 
stance. Large and subangular boulders occur in the gravel beds, 
and scattered along the valley below. 
As regards the character of the boulders, which make up the 
placer bed, they may consist of all kinds of rock, but more 
