10 
GEOLOGV 
servoir for the sustenance of industry and commerce along the whole line of the Pacific railroad. 
This carboniferous basin contains, in addition to the coal, an abundance of excellent sandstone for 
building bridges and embankments, good beds of limestone for the manufacture of lime, and also 
iron. Artesian wells will give an immense supply of water for agricultural or other uses, and it 
may be predicted that this region will be one of the richest portions in the Southern Stales of the 
Union. 
Immediately after crossing Delaware mount (latitude 34’, 44', 27" ; longitude west from Green- 
wich 96°, 57', 87".), which is formed of upkeaved and dislocated beds of Carboniferous limestone or Moun- 
tain limestone t') , whose direction is from south-south-west to north-north-east, we meet with Ao- 
rizontal beds of red and blue clay that belong to another geological epoch. This new formation, 
corresponding to that which European geologists have agreed to call the Trias , holds a very impor- 
tant position in the West; and it may be said, with some few exceptions — such as being some- 
times covered by a more modern formation, or replaced by carboniferous, devonian, or eruptive 
rocks — with these exceptions, the Irias may be said to form the whole of the immense square 
comprised between the 96"' and 114*'' degrees of longitude, and the 32'* and dS"" degrees of latitude; 
extending one arm to the Saull St. Marie, at the entrance to Lake Superior, of which it forms 
a part of the contour. 
This formation, which I was the first to notice and recognise in the West (See: A geological 
map of the United States and the British provinces of North America', page 42 ; Boston, July 1858.), at- 
tains a very considerable development, and, according to my observations, has a thickness of four 
or five thousand feet. The few observations as yet made on this American Trias , and its great ex- 
tent of surface, prevent the establishment of very certain divisions; but, from what 1 have seen, 
I will establish provisionally three principal divisions in these rocks. 
The Lower Division is composed , especially at the base , of red and blue clay ; the red pre- 
dominates as you ascend, and becomes of a vermillion color ; then red sandstone, with green spots 
and a very friable texture, a massive and sometimes schistose stratification, intercalates with the 
clavs, and finishes by entirely replacing them; but then the sandstone becomes argillaceous. Ge- 
nerally this sandstone is very fine-grained, like sand; but some beds are quite coarse, and re- 
semble a species of conglomerate. 
This Lower Group, which attains from two to three thousand feet of thickness, forms our whole 
route from Topofki creek to Rock Mary. I connect with this lower group the red sandstone that 
forms more than half the contour of Lake Superior 2), as well as that which forms the shore of 
*) In the vicinity of our camp A° 19, called in Whipples Report, Rranch of Topolki creek, at the wes- 
tern foot of Delaware mount, I found in a gray sandy limestone, an immense quantity of the remains 
of Encrinites, and a bed containing a great number of a fossil brachiopoda, called by James Hall in 
Stansbuiy’s Report on the Great Salt lake, page 412, Orthis umbraculum. De Verneuil and de Koninck 
who have examined the specimens , say that this Orthis is a Productus , and I give a figure and descrip- 
tion of it in the Chapter on Paleontology; see; Productus Delawarii (Plate V., fig. 3.). I found in the 
same bed a true Orthis also, but not sufficiently well preserved to be drawn or described. 
2) Dr. Charles T. Jackson first announced the existence of the Neu> Red Sandstone or Trias at Lake 
Superior. Struck w'ith the resemblance between the sandstone of Lake Superior and those of the shores ol 
Maine. New Brunswick and Nova Scotia, he did not hesitate to refer them to the same formation not- 
