196 The American Geologist. *^^'"'^^- ^^^^ 
of North Aincrica, Mr. E. S. Riggs ; March 18, "Extinct 
Mammals of North America," Mir. E. S. Riggs ; March 25, 
"Aims and Methods of Bird Study," Dr. N. Dearborn; 
April I, "Hawaiian Cruise of the Albatross,", Prof. C. C. 
Xutting; April 8, "The Fertilization of Flowers by In- 
sects," Dr. F. H. Snow; April 15, "Geographic Factors In- 
volved in the Rise of Chicago," Dr. J. Paul Goode ; April 
22, "How Rivers and Lakes IJecame Stocked with Fishes," 
Dr. S. E. ]\leek; April 29, "The liasketrv of California," 
Dr. J. \\'. Hudson. 
Kecent Study in Southeastern Michigan by F. B. 
Taylor shows that when lake Maumee was lowered the. 
waters fell to the level of the upper beach of lake Arkona, 
and that at. the close of this lake's existence the ice front re- 
advanced, pushing the point of discharge up the crest of 
the "thumb," thereby closing the Arkona outlet and raising 
the waters to the level of the Belmore beach of lake Whit- 
tlesey. 
The Goldfields District, Nevada, is a new mining camp 
of much promise, lying about 23 miles south of Tonopah. 
Mr. J. E. Spurr visited this district in November for the U. 
S. Geological Survey. The rocks are almost entirely vol- 
canic and are .probably of Tertiary age. The ores occur in 
rhyolytes and andesytes, though no definite vein systems 
were observed. The outcrops of the quartz bodies are irreg- 
ular, straggling, branching, and apt to disappear suddenly. 
They are sometimes nearly circular or crescentic, and fre- 
quently are rouglily lenticular and intermittent. Owing to 
the silicification of tlie volcanic rock in which it occurs, the 
(juartz itself is gray and jaspery. It is probable that this 
silicification is the work of hot springs and that these irreg- 
ular reefs represent the horizontal sections of columns of 
rocks traversed by rising columns of hot water. Had the 
rocks been strongly fractured we should have liad veins like 
those of the early andesyte at Tonopah, but the lack of such 
a fracture system at Goldfields resulted in this curious and 
rather unusual type of deposit. It follows that the quartz 
reels will probably extend deeper vertically than horizontal- 
ly, and so have roughly the nature of columns or pipes. The 
ores are often of very high grade. As an extreme example 
r^av be noted a shipment of 143^ tons from the Sandstorm, 
which Yielded $45,783 net when worked in a stamp mill, 
wliile the tailings still contained about $1,000 to the ton. 
From the McKane-Bowes lease on the Jumbo $600,000 was 
taken out in five months from a space that measured 100 
feet horizontally and 200 feet vertically on the shoot. The 
whole production of the camp has come from ores that 
range in value from $200 to $300 a ton. The values are all 
in gold, as silver is practically absent. 
