112 The American Geologist August, 1894 
Chandler mine at Ely, whioh has produced more iron ore, for 
the time it has been operated, than any other mine in the 
world. 
In the South Dakota exhibit was a natural section of the 
Homestake gold mine, at Lead City. This is the largest gold 
mine in the United States, employing 1.800 men. The section 
consisted of a perpendicular column of seven blocks of rock 
taken from the mine at intervals of 100 feet, showing the 
distribution of the ore in the rock. The cheapness of the 
smelting allows a good profit on the very low grade ore which 
is taken out. It has an average of $3.75 per ton, varying from 
.$1.00 to .$25.00 per ton, the annual output being about $4,- 
000,000. 
The crystalline rocks of Missouri were illustrated by 200 
hand specimens, collected by Messrs. I la worth and Lonsdale, 
of the Geological Survey, and by dressed blocks of granite 
from the granite companies. The specular ores were also ex- 
hibited by specimens. The Archean area of the state was 
shown hj a relief map covering an area of 250 square miles, 
the horizontal scale being 1 : 48,000; vertical 1:24,000. This 
area rises 1,500 feet above the sea. The line of the limestone 
anas surrounding it is 500-600 feet above the sea. The Ar- 
chean therefore rises from 900-1200 feet above the adjacent 
Cambrian areas, and about six square miles of this reaches 
1,800 feet above the sea. The rocks represented do not seem 
to belong to the true Archean, but resemble more in tout en- 
semble the crystalline rocks of the Norian. 
Other exhibits of crystalline rocks and associated minerals 
were seen from New Jersey, North and South Carolina and 
other states, but the writer happened to visit them when they 
were closed. 
Ward's systematic I'ock collection in the gallery of the 
Mining building, was by far superior to anything else of its 
kind seen in the exposition. This contained several thousand 
specimens dressed regularly to museum size, from all parts of 
the world. There was "petrosilex" from Dannemora, Sweden, 
appearing like the jaspilyte of Minnesota. There was every 
variety of volcanic rock as well as plutonic. including "quartz- 
porphyry tufa," from Zeiskywald, Ruchlitz and Wiesa. Sax- 
ony, and volcanic bombs two feet in diameter from Monte 
