OF NORTH AMERtCA. 
11 
the Bay of Fundy (Nova Scotia and New Brunswick), and also a part of the sandstone strata form- 
ing Prince Edward and the Magdalen Islands. In Virginia and New Jersey that part of the red 
sandstone which is without fossils and does not contain any gypsum belongs to this lower division , 
which closely corresponds to the Bunter Sandsiein of the German geologists, the Gres Bigarrds of the 
French, and the Upper New Bed Sandstone of the English. 
The Second Group, or Middle Division, is formed of beds of red clay; containing very often 
immense masses of white gypsum, amorphous, furrowed with veins of crystallized gypsum, with 
interposition of strata of magnesian or dolomitic limestone, and frequently beds of rock-salt or sa- 
liferous clay are found superposed upon the gypsum. The thickness of the beds in this Middle 
Group is about fifteen hundred feet. We met with it on our route constantly from Rock Mary to the Ar- 
royo Bonito, or Shady creek, with the exception of two points, where the direction taken by our ex- 
withstanding the contrary opinion of Bayfield and Logan, who had considered them as either Old Bed 
Sandstone or Potsdam sandstone. Dr. Jackson made a discovery in 1848 that confirmed the justice of his 
first view; he found at YAnse, near the mouth of Sturgeon river, in Keewenaw bay', beds of magnesian 
limestone filled with Pentamerus oblongus and consequently of the Upper Silurian epoch , much upheaced 
and surrounded by horizontal beds of the red sandstone of Lake Superior. In 1848 I made the com- 
plete tour of Lake Superior and carefully studied this question : my observations agreed entirely with 
those of Dr. Jackson and 1 at once adopted his opinion. 
Foster, Whitney, James Hall, Norwood, Whittlesey and Owen, in their Reports upon the Geology 
of Lake Superior published in 1851 and 1852, have maintained the old opinion as to the relative age 
of the sandstone formation of Lake Superior , synchronizing it with the Potsdam sandstone of the Now- 
York Survey, although their reasoning in support of this determination is entirely inconclusive. It may 
be thus resumed. The Potsdam sandstone with Lingula and Trilobites characteristic of the formation , is 
found on the rivers Escanaba , Menomonee and Sainte-Croix , to the south of the line dividing the waters 
of Lake Superior, Lake Michigan and the Mississippi river. A sandstone containing Lingula prima has 
been found in Tequamenon bay , Lake Superior, and therefore this sandstone is of the same age as the 
Potsdam. It is true , they add , that the sandstone of Lake Superior is never seen in intimate connec- 
tion with , and continuation of, the strata of Potsdam sandstone of the Escanaba and Ste. Croix rivers ; but 
the reason of this is found in the existence of a chain of eruptive rocks which was interposed before 
the deposit was formed. As to the mineralogical character and thickness of the formation, although they 
admit very striking differences, they are rejected as not being available in the determination of stratified 
rocks. To this I reply — That the Potsdam sandstone is found south of the dividing ridge referred to above , 
on the banks of the rivers Escanaba , Menomonee and Sainte-Croix , is not disputed ; but Foster , Whit- 
ney and Hall have forgotten to mention that the sandstone w ith Lingula prima found at Tequamenon bay , 
was a fragment taken from a boulder by Forest Shepherd in 1845, and that neither before nor since has 
any fossil been found in the sandstone strata en place of Lake Superior. Consequently Paleontology 
cannot be invoked to aid the determination of the age of this sandstone. As to the superposition , it is 
as we have seen in favor of Dr. Jackson's opinion , as well as the lithology and the thickness of the beds. 
Since then explorations, in which I participated during the year 1853, have proved that the sandstone 
formation of Lake Superior was a continuous series, and in direct relation w ith the beds of New Red Sand- 
stone which cover and form the majority of the immense Prairies bordering the rivers Missouri, Platte, 
Arkansas and Red river of Louisiana. In looking at the Geological Map (See: frontispiece.) it will be 
seen that Lake Superior formed a gulf resembling the bay of the valley of the Connecticut river , in the 
Triassic sea which enveloped the Paleozoic continent of North America. 
In regard to David Dale Owen, who since the death of Maclure and Vanuxem is the greatest geo- 
->i>. 
