OF NORTH AMERICA. 
97 
Upper Missouri ; the highest table-land is colored as Jurassic , and the Cretaceous is made to crop out 
lower down nearer the river and rests directly upon the formation called Trias. 
But the most striking feature of the map remains to be noticed. We find an area equal to that of 
all the States east of the Mississippi colored as Triassic. The section also represents this formation as 
enormously thick, and with four divisions corresponding to those in Europe. The color is extended 
on the map along the whole course of the Missouri down to Council Bluffs, and south into Texas, and 
is carried east so as to reach and border the southern shore of Lake Superior. The basis of this re- 
presentation is chiefly the occurrence of red gypseous strata along the False Washita and Canadian 
rivers. The upper limit of the formation is considered to be at the base of the so-called Jurassic strata 
of the Llano, and its lower upon the Carboniferous. 
The representation of this broad area as Triassic is made without the evidence of a single charact- 
eristic fossil, the principal support for it being the position and mineral characters of the strata. It is 
said that they are like those of Windsor and Plaistcr Cove, N. S., which were supposed to be Triassic 
but have since been shown by Mr. Dawson to be Carboniferous"). Hence the similarity indicates a Car- 
boniferous age rather than Triassic. The limit of the formation above or below, although perhaps well 
defined at one point, may not bo at others, or may be very different; the red color of the strata — 
the only guide — being the result of chemical changes and not of original deposition. The lower limit is 
not clearly defined, and there are no outcrops or uplifts of the strata sufficient to reveal the whole series. 
The thickness, therefore, cannot be accurately stated. 
The entire absence of fossils from these strata, so far as known, and our slight knowledge of the 
line of separation between them and those of known ago, and the impossibility of determining their thick- 
ness, render it premature, at least, to assign them to the ago of the Trias, and to partition them into 
groups corresponding to those of the formation in Europe. We may with equal reason call the strata 
Jurassic, Liassic, Triassic and Permian, or either of them, as Triassic alone. It would be most in 
accordance with the indications to refer them to the Cretaceous and Carboniferous, the two adjacent formations 
above and below. 
But even if the gypseous strata along the Canadian were proved to be of Triassic age, it does not 
follow that those along the Upper Missouri, a thousand miles away, are of the same period. According 
to published reports the strata along the river are Cretaceous, and there is no evidence of the presence 
of the Trias. Neither is there any evidence of the extension of the Lake Superior sandstone across Wis- 
consin into Iowa and out to the Missouri, as if the formation occupied an > east and west valley in the 
granite. Such a representation is at variance with published records, and these surely should bo regarded 
in the absence of personal observation. It is hardly necessary to state that the sandstone of Lake Superior 
has been examined by three separate geological corps, — Messrs. Whitney and Foster with the assist- 
ance of Prof. James Hall, by D. D. Owen, and by Sir W. E. Logan knight of the Legion of honour of 
France — and after several years of exploration in that region, all arrive at the conclusion that the 
sandstone is not the ISew tied, but is the equivalent of the Potsdam sandstone of New York. Prof. James Hall 
has announced the conclusion also in a notice of a former map by Mr. Marcou. 
There is here a disregard of published results , and an audacious attempt at generalization , which has 
seldom been equalled. The fact that Mr. .Marcou's map is widely circulating in Europe just such American 
Geology as this, has made it the duty of the science of the country to protest against its being accepted abroad, 
notwithstanding its publication under the sanction of the Geological Society of France. 
") Acadian Geology, by J. W. Dawson. Edinbourgh, 1855. 
The motives that produced the above criticisms of Hall, Whitney, and Blake, and led 
James U. Dana to publish them in the American Journal of Science and Arts, are too evident to re- 
quire an answer. Hall was not so courageous as his two assistants, preferring the shelter of the 
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