54 OF FOSSIL SALT AND GYPStrM- 
"invariably bounded by precipices of red-sand-rock, forming 
"the river bluffs. In the valley between these, incrustations of 
" nearly pure salt are often found covering the surface # to a great 
il extent in the manner of thin ice, and causing it to appear 
"when seen at a distance, as if covered with snow." "The 
Canadian, like Red River," says Mr. Nuttall, " always continues 
red and muddy, and is often impotably saline." Wherever there 
are salt springs within the limits of the United States, the rocks in 
the neighbourhood are sandstone, clay, or limestone with organic 
remains, and in many cases they embrace beds of gypsum. 
Fossil salt abounds also in Mexico, and South America. 
The saliferous sandstones furnish another example of that too 
hasty generalization which has so often marked the history 
whilst it has arrested for a time, the progress of geology. There 
is a general agreement in the composition, structure, and aspect 
of these rocks. They contain imbedded masses of salt and gyp- 
sum. It was inferred that they are of the same age, and were 
produced by the operation of the same causes in all parts of the 
world. But when even such as are not very remote from each 
other, and are supposed to be nearly contemporaneous, are care- 
fully compared, wide discrepancies appear. Those of England are 
confined to a single stratum or formation which hardly admits of 
a subdivision, and in" which organic remains, if they occur, are 
very rare. In France and Germany they extend through at least 
three different strata, the keuper, muschelkalk, and bunter-sand- 
stein of the German geologists, of which the last only has an inti- 
mate agreement with the new-red-sandstone, and the second, 
abounding in organic remains, is regarded by Brogniart as the 
proper repository of the salt. When the test furnished by the 
imbedded remains is applied to them, the saliferous strata of Spain^ 
France, and Poland are seen to separate widely, proving that the 
causes which have operated in the formation of these deposits of 
salt and gypsum, have been repeatedly active upon the surface 
of the globe, and in places and at epochs far remote from each 
other. In the state of New York the beds affording these 
minerals, are separated by three intervening strata. 
32. Next below the new-red-sandstone is the magnesian or 
conglomerate limestone. To this succeeds in some parts of Eng- 
land, another red-sandstone, supposed to be the equivalent of the 
Rothe-liegende, and next to this are the coal measures, the inde- 
pendent coal formation of Werner. This embraces, with two or 
three very unimportant exceptions, all the seams of workable coal 
that exist on the Island of Great Britain. Of course it furnishes 
nineteen-twentieths of the fuel consumed for domestic purposes, 
by the population of the country: keeps two hundred and fifty-three 
iron furnaces of gigantic dimensions, besides innumerable smaller 
ones, employed in other metallurgic operations, in blast, from one 
year's end to another: puts thousands of steam engines in motion, 
and contributes more than any other one thing to the wealth and 
