APPENDIX. 359 



visit; but the nature and position of the rock strata and soils, 

 and the general aspect of the country, do not justify the conclu- 

 sion that the bed is of much thickness or extent. Valuable beds 

 may be discovered, however, by exploring this formation. This 

 coal has a shining black color, a slaty structure, inflames readily, 

 burning with a bright flame. It is very fragile where exposed to 

 the weather, falling into fine fragments. Hence, a very black 

 color has been communicated to the contiguous and overlaying 

 soil, which is manifestly more or less the result of disintegrated 

 coal. 



Detached fragments of coal, corresponding in mineral charac- 

 ters with the above, are occasionally found around the southern 

 shores of Lake Michigan. The inference, as to the existence of 

 coal around the shores of this lake, is obvious. And we are led 

 to inquire: Does the La Charbonni^re formation of coal exist in 

 the sandstone and limestone strata forming the table-land between 

 the Illinois Eiver and Lake Michigan, and reappearing around the 

 basin of the latter, but at such a depression below its surface as 

 to elude observation ? And, if so, does not this coal formation 

 extend quite across the southern portion of the peninsula of 

 Michigan? The secondary character of the region alluded to, 

 so far as observed, the horizontal and relative position of the 

 strata, and the general uniformity which is generally observed in 

 the species and order of the coal measures, favor this suggestion. 



i. Soda. 



1. Muriate of Soda. 



No traces of salt are known to have been discovered in those 

 parts of the territory of the United States situated north of lati- 

 tude 46° 31' (which is that of the Sault Ste. Marie) and east of 

 the Mississippi Eiver. 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 in- 

 formation, that, in the natural order of the rocky and earthy 



