166 The American Geologist. March, 1892 
the close of the Gault, or Shasta period, as Dr. Becker has lately 
affirmed.* A small unconformity undoubtedly exists, due in 
part to the eruption of the serpentine, and in part to an uplift 
accompanying it. The extrusion of such an immense body of 
igneous rock as that near Knoxville, ranging from three to five miles. 
in width, and twenty miles long, must have pushed back and 
tilted the Knoxville shales to a considerable extent. 
I see no other way but to return to the views of Prof. Whit- 
ney with regard to the gold belt of the Sierras, that is, to a 
post-Jurassic upheaval. This upheaval accompanied by granite 
and affecting the region of both systems of mountain ranges. 
simultaneously, gave rise at least to the Coast Range with its 
series of metamorphic rocks. 
Concerning the evidence of the fossil Aucella, since standard 
authorities differ in regard to its exact time range, I see no reason 
why it might not have existed during the Jurassic in the Sierra 
region, and, since its geographic range is of great extent, have 
returned again to regions where favorable conditions existed, 
after the great upheaval which separated the metamorphic rocks 
of both the Sierras and Coast Ranges from the lowest Cretaceous. 
RELATIVE ABUNDANCE OF GOLD IN DIFFERENT 
GEOLOGICAL FORMATIONS. 
W. P. BLakeE, Shullsburg, Wis. : 
In the interesting notice of the ‘‘Universality of Gold” by 
Dr. Everette in the November issue of the AMERICAN GEOLOGIST, 
page 331, he says: ‘Therefore gold may be sought for in every 
geological horizon, and has thus been found in more or less pay- 
ing quantities from the very earliest rocks up to the recent allu- 
vial and drift formations,” a statement which may be accepted as 
correct, but he proceeds to state :— 
‘However, in those veins of quartz which are found in the 
Cambrian and Lower Silurian strata, gold in the metallic state in- 
termixed amongst the quartz is found in far greater commercial 
quantity than in any other of the preceding or subsequent geo- 
logical horizons. Wherever gold has been found in very large 
quantity in either vein or placer form, it has been found to be 
*Bull. Geol. Society of America, Vol. II, p. 206. 
