264 
stick into such mud, bringing up a stream of marsh gas bub- 
bles, has opened a gas well on a small scale. 
This view of Gas-Genesis is but a corollary of my theory 
of Coal-Genesis, laid before this Lyceum, Jan. 10, 1870, 
which makes the oxidating action of ferrous sulphate on car- 
bon the cause of formation of coal, together with its accom- 
panying iron minerals. It will be remembered that coal and 
marsh gas are usually concomitant, in depth at least. 
At the epochs of deposition of these rocks then, the basin 
of the great North American continental lagoon was filled to 
varying depths with ferruginous mud, highly charged with 
organic matter, which after being covered with other beds (of 
sandy character) during the process of induration into shales 
(a process without doubt due to the same action) underwent 
an internal fermentation, such as I have described. The car- 
bonic acid, always formed at the same time, chiefly disappears, 
from its solubility in water, through which it is transferred to 
the bases, lime, magnesia and ferrous oxide, always abundant | 
in such rocks. 
3. ENGINEERING POINTs. 
In the handling of these gases, ordinary engineering, even 
ordinary gas-engineering practice, will not furnish rules of 
much value. The enormous pressures to be dealt with, pres- 
sures moreover of a medium which is so subtile, will require 
special appliances and contrivances. Probably with regard 
to these it is not becoming t@ me, belonging toa different 
profession, to offer anything more than mere suggestion, and 
I shall therefore be satisfied with pointing out here what ap- 
pears to me a new and inviting field for the scientific engineer. 
After the gas has been controlled and confined, other engi- 
neering problems come in; inasmuch as many of these wells 
will be so situated that it will be highly desirable to convey 
the gas to long distances through suitable ducts. It will be, 
in fact is now, a problem to be determined by experiment, as 
to proper relations of length and diameter of duct, to such 
heavy pressures. For pressures of a few inches of water, all 
that is usually dealt with in gas-engineering, an empirical 
