42 The American Geologist. July, 1^99 
mained in the soil of the land surface, gradually accumulating, 
becoming especially abundant where some rich quartz vein was 
being eroded. While the evidence collected in the field indi- 
cates some denudation, it does not prove a very long erosion 
interval at this horizon, yet considerable gold must have ac- 
cumulated in the thin soil over the ancient lava plain. 
Now the land went down beneath the sea, and the immense 
mass of Jurassic black slates was deposited over the green 
diabase. As each portion of the land surface successively 
foimed the shore-line, the waves swept away the soil, laying 
bare the solid rock in places, but in others leaving a thin coat- 
ing of the ferruginous clay. This, together with its golden 
contents, was especially protected from marine erosion in shal- 
Icv/ depressions such as those in which the "pockets" are now 
geneially found. Indeed, one who has studied the concentrat- 
ing power of the waves, as I have on the gold-bearing beach 
of the peninsula of Azuero, Rep. of Col., would readily com- 
prehend the probability of the ancient sea having swept the 
gold from broad areas of the sinking land surface, and concen- 
trated it into certain very limited depressions, yet even there 
almost removing all of the lighter clay and sand. In this way 
would be produced the deposits as they now actually occur, 
namely, as a heterogeneous agglomeration of gold grains and 
what appears to be land-surface debris. 
Old miners to whose consideration I have presented this 
hypothesis, have reminded me that the gold in the "pockets" 
averages decidedly coarser than that of the quartz veins and 
amygdaloids. At first thought this might prove fatal to the 
theory, but does not. The gold has probably been changed 
from its original very fine condition in one, or perhaps both, of 
two ways, as follows: 
(i) It may have been dissolved by surface waters and re- 
deposited in practically the same place. Whether this ever oc- 
curs, as, for instance, in alluvial gravels, is a mooted question 
at present. California contains some evidence on the subject, 
which I cannot discuss now. However it may be, I do not 
think that to any great extent this theory is applicable to the 
"pocket" deposits. 
(2) The miners say the gold has been melted. Certainly, 
the condition of many of the pockets favors the idea that since 
