No. 275.] 37 
depths, to which all these phenomena may be ascribed. The access of 
water to these beds of sulphuret of calcium, causes its decomposition, 
and as a necessary consequence, gaseous sulphuretted hydrogen is evolv- 
ed. This 2;as, in its course to the surface, is partly absorbed by water, 
while, from its reaction upon that liquid, a portion of sulphuric acid 
is also formed, a result which we constantly observe in the laboratory. 
The sulphuric acid thus formed, acting upon the upper strata produces 
sulphate of lime, and causes the evolution of carbonic acid, a substance 
which is almost always found in the mineral waters of the west. 
This view appears to me conformable to the known laws of chemis- 
try, and is sustained by the facts which are presented. The only as- 
sumptions, are the existence of the sulphuret of calcium, in quantities 
sufficient to produce these results, and the agency of water. In regard 
to these, I will here only remark, that they are supported by the same 
train of argument, that is brought to bear upon the chemical theory of 
volcanic action; of which action, many evidences, in addition to those 
above noticed, are presented in various parts of our State. 
Earthy Minerals. 
61. The minerals included under this class are composed chiefly of 
one or more of the earths proper; frequently, however, containing some 
alkali, alkaline earth, acid or metallic oxide. They have also sometimes 
been termed earthy compounds or stones, and they are probably more 
interesting to the mineralogist than those belonging to any other class. 
In some cases, the composition of these minerals is very complex, 
which renders their analysis difficult. At the same time, this very cir- 
cumstance makes their careful study the more important, and as slight 
differences in chemical composition not unfrequently form the basis of 
specific distinctions, increases the chances of new discoveries. To show 
that I have not been inattentive to this part of my work, I beg leave to 
state, that a portion of every season since its commencement has been 
devoted to the collection and study of the minerals belonging to this 
class. Seven or eight weeks of the last summer were spent among the 
rich localities of Orange county, in company with my friend. Dr. Wm. 
Horton, who is so well acquainted with the minerals of that county, 
and who was then engaged in examining its geology as the assistant to 
Prof. Mather. I should do injustice to my own feelings, did I not thus 
publicly acknowledge the important assistance which I have at various 
times received from Dr. Horton, who has perhaps done as much, if not 
more, than any other individual towards bringing into notice the vast 
mineral resources of Orange county. 
