No traces of salt are known to have been discovered in those parts of the territory of the United States situated north of latitude 46° 31´ (which is that of the Sault Ste. Marie) and east of the Mississippi River. The great secondary formations which pervade the western country cease south of this general limit, and with them terminate the salt springs, the gypsum beds, the coal measures, and other connected minerals which are generally found in association. It is one of the most important facts which the science of geology has contributed to the stock of useful information, that, in the natural order of the rocky and earthy deposits, muriate of soda always occupies a position contiguous to that of gypsum. This intimate connection between the sulphate of lime and the muriate of soda, enables us, by the discovery of the one, to predict, with considerable but not unerring certainty, the presence of the other. It adds weight to an observation first made among the salt formations of Europe, to find its general correctness corroborated by the relative position of these substances in the United States. These remarks will apply particularly to the salt formations of New York, and to some portions of the muriatiferous region of Virginia and the Arkansas.
There appears to be a salt formation extending from the northwest angle of the Ohio through Michigan, for a distance of two hundred to three hundred miles. It commences in the Seweekly country, passing around the Sandusky River of Lake Erie, where an extensive bed of granular gypsum has recently been discovered, and continues, probably, northwest, so as to embrace the Saganaw basin, and reach quite to the end of the peninsula, and embracing, perhaps, the Gypsum Islands of Lake Huron, ten miles northeast of Michilimackinac. All the brine springs and gypsum beds noticed in the region are situated in the line of this formation.
During the fall of 1821, a number of gentlemen at the Island of Michilimackinac united in the expenses of a tour for exploring the Skeboigon River, a stream which originates in the peninsula of Michigan, and flows into Lake Huron opposite the Island of Bois Blanc. The particular object of this party was to ascertain the precise locality of certain salt springs reported to exist upon that stream. They proceeded to the places indicated, and examined several springs more or less impregnated with salt, but reported that, owing to the jealousy and hostility of those bands of Indians who were found upon that stream, they were not enabled fully to accomplish the object in view.
There are several salt springs reported to exist near the Indian village of Wendagon, on the Sciawassa River, and others on the Titabawassa River, the principal tributaries of the Sagana. Little is, however, known respecting these springs, but the water is represented to be so strongly impregnated, that the Indians manufacture from it all the salt necessary for their villages.
Grand River Valley has also been mentioned among the localities of salt water and gypsum rocks.
Hints may thus be derived of value to the future commerce of the country. Scarcely any of the new states are without indications of the existence of salt. Every day is adding to the number of localities.
In the region west of the Mississippi, I was informed that salt occurs, in the crystallized form, in the territories of the Yanktons, who inhabit the flat country at the sources of the River St. Peter's. In certain parts of these plains, the salt exists on the surface. It is mixed with earth, in specimens brought to me, but crystallized in cubes, very imperfect, of a gray or grayish-white color. The Indians scrape it up from certain parts of the prairies or plains, where the salt water is prevented from draining off.
2. Alkaline Sulphate of Alumina.
This salt exists, in the form of efflorescences, in the cavities and fissures of rocks along the southeast parts of the shores of Sagana Bay, Lake Huron, and in the argillaceous formations at Erie, on Lake Erie, Pennsylvania.