T. S Hunt— Celestial Chemistry. 133 
meval ocean, that all limestones and dolomites have been gen- 
erated. These, apart from the coaly matter, hold, locked up 
and withdrawn from the aérial circulation, an amount of car-. 
bonic acid which may be probably estimated at not less than 
200 atmospheres equal in weight to our own. That this 
amount, or even a thousandth part of it, could have existed at 
any One time in our terrestrial atmosphere since the beginning 
of life on our planet is inconceivable, and that it could be sup- 
plied from the earth’s interior is an hypothesis -equally un- 
tenable 
I was therefore led to admit for it an extra-terrestrial source, 
and to maintain that the carbonic acid has thence gradually 
come into our atmosphere to supply the deficiencies created by . 
chemical processes at the earth’s surface. Since similar pro- 
cesses are even now removing from our atmosphere this indis- 
pensable element, and fixing it in solid forms, it follows that 
except volcanic agency, which can only restore a portion of 
what was primarily derived from the atmosphere, there are on 
earth, besides organic decay, only the artificial processes of hu- 
man industry which can furnish carbonic acid; so that but 
for a supply of this gas from the interstellary spaces now, as in 
the past, vegetation, and consequently animal life itself, would 
fail and perish from the earth, for want of this “ food of planets.” 
Such were the conclusions, based on an induction from the 
facts of modern chemistry and geology, which I enunciated in 
my papers in 1878 and 1880, already quoted in the first part of 
this essay. I was at that time unacquainted with the Hypothe- 
sis of Newton, and with his remarkable reasoning contained in 
the 41st proposition of the third book of the Principia, in which 
of planets,” and, in a sense, “ the material principle of life.” 
have thus endeavored to bring before the Philosophical 
the almost forgotten views of Newton. It is with feelings of 
