ae ee a an Sik ie. 
J. J. Stevenson—Fox Hills Group of Colorado. 369 
Art. XLIV.—Note on the Fox Hills Group of Colorado; by 
J. J. STEVENSON, Professor of Geology in the University of 
New York. 
Nor far from thirty miles below (north) Denver, St. Vrain’s 
Creek enters the South Platte River from the west. The 
Thompson enters from the same side several miles above 
Evans, or about forty-five miles below Denver; and the Cache 
La Poudre, in like manner, enters somewhat more than fifty 
miles from Denver. The towns of Evans and Greeley lie close 
together, the former being on the South Platte River almost 
fifty miles from Denver, 
In 1873, I visited this region and made some observations, 
which were published shortly afterward. As the conclusions, 
which I then reached, were called in question, I took oceasion 
before entering the field in 1878 to revisit the locality. 
A line of bluffs begins on the west side of the South Platte 
River at a little way below the mouth of St. Vrain’s Cree 
and continues until within a mile or two of Thompson Creek. 
This bluff is more or less distinct on the north side of the 
St. Vrain for nearly four miles from its mouth. Similar bluffs 
are conspicuous along the northerly bank of Thompson for 
several miles, and ean be traced thence to near the Cache La 
Poudre without any difficulty. 
A low bluff-like ridge, lying at from one to three miles from 
the river, begins at Platteville on the east side of the stream, 
and is easily followed to a considerable distance northeastward 
rom the town of Evans. 
In the bluffs lying on the west side of the Platte, the rocks 
dip gently northward. On the opposite side the dip is insig- 
nificant; a very gentle anticlinal was observed at Platteville, 
. and the rocks are almost horizontal or possibly dipping slightly 
toward the north at four miles southeast from Evans, _ 
e West side of the South Platte River.—Following the 
grade of the Colorado Central Railroad on the west side of the 
river, one finds, somewhat more than four miles above Evans, 
an outcrop of bright yellow, very friable sandstone, forming a 
broad band on the bluff. Fragmentary outcroppings of the 
Same rock were observed farther down the river, but here for 
the first time the exposure is satisfactory. : 
n the Thompson, the exposure ends with the curving bluff 
at probably five miles from the river, and the dip along the 
Stream is insignificant. : : 
As already stated, the bluff begins again on the south side 
of the Thompson probably two miles from that stream, an 
is continuous thence to within a short distance of the St. Vrain. 
