No. ^75. J 
analogous ones. These products throw the greatest light upon the ori- 
gin of the saline materials of the group, and of the whole group we 
would say, were this not a practical report. These products furnish 
a series of facts, when well considered, will contribute more towards 
connecting those causes called volcanic action, now in operation, with 
similar causes, which must have existed and operated from the time that 
there was a solid crust, but operating with materials differing from those 
now generally used, would produce different products, and the greater 
the difference of material, and the greater the difference of age from 
causes hereafter to be mentioned, the greater would be the difference in 
the products; and hence the great difficulty of recognizing the products 
of volcanic action beyond a limited period. 
That difference of age causes the products of volcanic action to be 
different, is evident in the ancient province of Auvergne, in France. 
There there are three distinct eras or ages of volcanic action, each dif- 
ferent from the other. The first or oldest, formed of porphyries and 
other feldspathic rock; the second of basalts; the third and last of " gray 
lavas." This latter kind alone in currents and connected with craters. 
When, too, we bear in mind that the state of the earth's surface was 
wonderfully different from which it now is, and at no very remote 
period; nay, that even in comparatively recent times, "the mountains 
were brought forth," we are not surprised that we so quickly find our- 
selves at fault when we endeavor to extend our actual knowledge of 
known volcanic action beyond the tertiary periods. 
The great mass which encloses the " gypsum beds," is the " calciferous 
slate" of Prof. Eaton, a name which he had likewise applied to a 
somewhat similar, but high fossiliferous deposit which is placed between 
the layers which contain the iron ore beds and the concretionary or Lock- 
port limestone mass. The two slates so different from each other were 
considered to be one and the same; nor need we wonder at their union, 
since few are the observers that have not fallen into a like error. These 
" slates" of the gypseous beds, bear a strong resemblance in their drab 
colour, the thinness of their layers, by their composition of carbonate 
of lime and argillaceous matter with the deposits which form the jilains 
of the table lands of Mexico, and the saline materials of both point 
to causes of a like nature. 
The gypsum in no part of the Third District form layers or beds; on 
the contrary, it occurs in insulated masses, as though the particles of 
each mass had been attracted by a common centre, but greatly modified 
by disturbing causes. There seems to be tw(5 distinct ranges of " plas- 
