1 68 The Americaji Geologist. Marcii, 1900 
process continued until a rock with a moderate amount of 
silica came to be a rock of almost pure silica. Since the 
latter has been mostly in solution it assumes the flinty na- 
ture and appearance. The fact that the material has been 
in solution is supported by the presence of the silicified 
fossils whose originals were calcareous, while the pres- 
ence of the fossils themselves argues for the origin of the 
rock as a calcareous sediment. 
We realize perhaps as fully as any one that in this paper 
we have not solved the problem but merely stated and de- 
scribed the conditions. How and why a quartzyte layer 
should be present in this particular part of the Niagara is 
still as great a m\stery as the deposition of the immense 
quantities of the sulphides of zinc and lead in the limited 
region of the Galena limestone and not uniformly in all of it. 
THE ESMERALDA FORMATION.* 
By H. W. Turner, Washington, D. C. 
In Esmeralda county, Nevada, there are extensive deposits 
of Tertiary sediments which contain, at some points, abundant 
plant and animal remains. This series may be designated the 
Esmeralda formation, taking its name from the county in 
which it occurs. Near these lake deposits, at the north end of 
the Silver Peak range, there are beds of coal and the first pub- 
lished notice of these Tertiary beds appears to be that of the 
mining engineer, Mr. M. A. Knapp, describing particularly the 
coal deposits, f Mr. Knapp collected some moUuscan remains 
near the coal beds and these were examined by Dr. J. C. Mer- 
riani, of the University of California, who considered the shells 
indicative of fresh water and possible Miocene in age. In 1897. 
Mr. Walcott, director of the U. S. Geological Survey, visited 
the region and took some excellent photographs of the beds 
*Published by permission of the Director of the U. S. Geological 
Survey. 
tThe Coal Fields of Esmeralda County, Nevada. Mining and Scien- 
tific Press, San Francisco. Vol. 74, 1897, p. 133. 
It might be noted however, that fossil fish from this formation were 
collected by J. E. Clayton and W. P. Blake, but no determination of 
these fossils appears to have been put in print. 
