312 
GEOLOGY OF THE FOURTH DISTRICT. 
often marked by a black and red deposit, as well as sometimes a whitish stain upon the rock 
or in the bottom of the spring. The flow of water is feeble, and it is less strongly impregnated 
with gas. 
Such being the fact in relation to these springs, we are to look for some general cause why 
those in the Onondaga salt group are so much more copious, and strongly charged with gas, 
than any others. Since also there is no general line of disturbance or uplifting along the 
outcropping edge of this group, we cannot attribute their origin to any source below the rock 
itself; for if so, they would as probably be in other situations a little farther north or south ; 
but as the facts stand, it is upon the very margin of this formation where they occur. The 
jointed and fissured limestone above affords a passage for the water from the surface, which 
falls down upon the impure argillaceous limestones beneath, and passes through these to an 
impervious stratum, when it rises to the surface. 
Now all we have to account for, is the source of the gas, and by what process the water 
becomes thus charged? The rock contains iron pyrites, often very intimately blended ; and 
on burning in the kiln, a large quantity of pure sulphur sublimes, and lodges upon the stones 
about the top. It is impossible, perhaps, to say that this is in a pure state in the rock; but 
may it not probably be in some other combination than with iron, and one which may be more 
readily decomposed by water and atmospheric agents ? Since sulphur is known to be diffused 
through this rock, either in a free or combined state, it is very rational to suppose that it 
enters into combination with the hydrogen of the water, and thus produces the phenomena 
of gas springs. 
The decomposition of sulphuret of iron, in moderately damp situations, gives origin to 
sulphate of iron ; but this could not exist in the water of these springs, though there is usually 
present some other sulphates, as the sulphate of lime or of magnesia. In the higher shales, 
which all contain iron pyrites, we find the decomposition leaving an iron stain, and often 
sulphate of iron, almost always sulphate of alumina, and always sulphate of lime, which 
forms in small crystals upon the slaty laminae. These products are the results of the decom¬ 
position of iron pyrites, in districts and situations where they are exposed to the weathering 
influences, but where there is not sufficient water to form springs. They do not differ, so far 
as they go, from those of sulphuretted hydrogen springs. I have made no detailed examina¬ 
tion, but there is little doubt but an analysis of these dry efflorescences would prove them to 
contain all the products of sulphur springs, or at least to bear an equal comparison to the 
products of one spring with another. During rains, the odor of this gas is perceived from 
the situations where these dry efflorescences appear, though not at other times. 
On the Niagara river, a short distance above Lewiston, there is a copious spring issuing 
from the cliff, highly charged with sulphuretted hydrogen gas, and the water impregnated with 
sulphate of magnesia; and judging from some incrustations upon the stone, it contains both 
the sulphate and carbonate of lime. Now this spring has its origin in a highly magnesian 
limestone, which is also charged with iron pyrites. In sheltered situations under the cliff, 
this rock is rapidly decomposed, and produces sulphate of magnesia, with a little sulphate of 
iron and carbonate and sulphate of lime. These substances can be obtained to the amount of 
