176 
DESCRIPTIVE MINERALOGY. 
the water several feet into the air; but the gas soon diminished in quantity, and can now be 
observed rising only in small bubbles through the bed of the stream (see page 137). 
The carbonic acid which is given out by various mineral waters is sometimes in a free 
state, as is the case at Ballston and Saratoga, where large bubbles rise through the water at 
regular and short intervals ; or it holds in solution various bases in the form of bicarbonates, 
which, as soon as a portion of the acid is evolved, are deposited as simple carbonates. Such 
phenomena are observed at the brine springs in Onondaga county and elsewhere, and at those 
which are called petrifying springs , of which there are many in Western New-York. 
As I have already noticed this subject at length under the head of mineral springs, it will 
be unnecessary to add further particulars (see page 134). 
ATMOSPHERIC AIR. 
Atmospheric Air. Shepard and Dana. — Reines Atmosphar-Gas. Mohs. 
Description. Gaseous, transparent, tasteless and inodorous ; sparingly absorbed by water. 
When in large masses, it reflects a blue colour. Its specific gravity is taken as the standard 
for all gases and vapours, and is therefore 1000. It is about 780 times lighter than water at 
40.5 Fahr., when water is at its greatest density, and is then also 10,600 times lighter than 
quicksilver. Kane. 
Composition. The constituents of atmospheric air, are nearly as follows, viz: Nitrogen 
gas 75.88, oxygen gas 23.04, watery vapour 1.03, carbonic acid 0.05. These ingredients, 
however, are thought to be rather in the form of mixture than of true chemical combination. 
Their proportions are moreover liable to slight variations from general and local causes. 
Atmospheric air is sometimes given out through the clefts of rocks, and is associated with 
the other gaseous minerals which are peculiar to certain springs. Thus Dr. Daubeny states 
that the gaseous matter evolved by the water of the Lebanon spring consists of about fifty 
parts of atmospheric air and fifty parts of nitrogen, in the hundred. Small quantities of air 
have also been detected in several of the Saratoga springs. In this case its origin is probably 
the same as that of the other gaseous contents. The air which is uniformly found in the 
water of fresh water springs may also, I think, be referred to some deep seated and general 
agency. 
That atmospheric air does find its way into the interior of the earth, through the cracks and 
fissures with which its crust is every where intersected, the large cavities it so frequently 
envelopes, and perhaps through its porous and permeable structure, is an idea which seems to 
be sufficiently well sustained. If such is really the fact, it will not be difficult to account for 
the occurrence of atmospheric air, and occasionally of pure nitrogen, in the waters of certain 
springs. To account for the latter, we have only to suppose that certain processes, occa¬ 
sioning the abstraction of oxygen from common air, are going on in the interior of the earth.* 
* See Dr. Daubeny’s Report on Mineral and Thermal Waters. Reports of the British Association for the Advancement of 
Science, 1836. 
