I 
AIR 
repeated experiments ; by putting up feeds into glafs 
bottles, and fealing the bottles hermetically, and in 
fix months thofe feeds have loft their growing quality; 
whereas part of the fame feeds which were kept in 
bags, grew at the age of two years ; therefore it fhould 
caution perfons not to exclude the air from their leeds, 
if they intend they fliould grow. 
Another inftance of the ufefulnefs of the air in vege- 
tation, is the Sedum, which will pufli out roots with- 
out earth and water, and live for feveral months : and 
fome forts of Aloes, if hung up in a room entirely 
lecured from frofts, will remain frefh for fome years, 
though they will fenfibly lofe in their weight. 
Air is capable of penetrating the porous and fpongy 
parts of plants, and being there contrafted, and di- 
lating itfelf again. 
The air operates alfo within the bov/els of the earth, 
and by its fubtilty perfpiring through the pores, affifts 
in the rarefaction of the crudities of the earth, and in 
the diipelling all fuperfluous moifture, entering into 
the very pores and veins of the trees, plants, herbs, 
&c. carrying along with it thofe fairs contained either 
in itfelf, or lodged in the earth •, which fairs or juices, 
are altered according to the feveral figures or dimen- 
fions of the different ftrainers or veffeis of thofe feve- 
ral plants, which grow upon the fame fpot of earth, 
which is fo impregnated with thefe fairs : and thence 
thofe varieties in tafte and fmell proceed, notwith- 
ftanding-they all receive their nourifhment from the 
fame frock that is lodged in the earth. 
The air alfo affects the branches, leaves, and flowers 
of trees, plants, and herbs, entering and perfpiring 
through them, and even through the bark and body 
of the tree ; and by the fame kind of fubtilty it does, 
by its refrefhing breezes, moderate the intenfenefs of 
the fun-beams, cooling, cheating, blowing, opening 
and extending all the offspring of nature. 
The air fixes and infinuates its aerial fubftance into 
the liquid fap of vegetables : and as all the agitations 
in nature proceed from the contrariety of parts inha- 
biting together, in this, aerial and liquid fubftances 
being mixed, caufe this agitation and motion in ve- 
getables, or, more properly, fet it all into a ferment 
(whether it be in the roots, or in the Item) ; and it 
rifes by co-operation of the fun (which is the third 
agent in vegetation) up to the top of a tree, &c. as 
liquids rife by fire to the top of the containing vefiel. 
This air, we find, produces a vibratory motion in fe- 
veral bodies •, and particularly in plants, the air vef- 
feis thereof do the office of lungs : for the air con- 
tained in them, fometimes contrafling, and fometimes 
expanding, according as the heat is increafed or di- 
mmifhed, preffes the veffeis, and eafe them again by 
turns ; and thus promotes a circulation of their juices, 
which could fcarce be otherwile effefted. 
Air, fays the learned Dr. Hales, is a fine elaftic fluid, 
with particles of very different natures floating in it, 
whereby it is admirably fitted by the great Author of 
nature to be the breath or life of vegetables as well 
as animals, without which they can no more live nor 
thrive than animals can. 
As a proof of the great quantities of air in vegetables, 
he refers to the third chapter of his excellent treatife 
of Vegetable Statics, where he fays, in the experi- 
ments on Vines, the great quantity of air was vifible, 
which was continually afcending through the fap in 
the tubes ; which manifeftly fhews what plenty of it 
is taken in by vegetables, and is perlpired off with 
the fap through the leaves. 
He adds feveral experiments, as to an Apple branch, 
Apricot branch, Birch, and other plants, to prove the 
fame thing. 
And Dr. Grew has obferved, that the poqfo are fo 
large in the trunks of fome plants, as in the better 
fort of thick walking-canes, that they are vifible to 
a good eye without a glafs ; but with a glafs, the cane 
feems as if ftuck at top full of holes with great pins, 
fo large as very well to refemble the pores of the fkin 
in the ends of the fingers and ball of the hand. 
In the leaves of Pines, they are likewife through a 
A I R 
glafs a very elegant fhew. Handing almoft exa&ly in 
rank and file through the length of the leaves. 
Whence it may be thought probable, that the air 
freely enters plants, not only with the principal fund 
of nourilhment by the roots, but alfo through the 
furface of their trunks and leaves, elpecially at night, 
when they are changed from a perfpiring, to a ftrongly 
imbibing ftate. 
Dr. Hales likewife tells us, that in all thofe experi- 
ments that he tried to this purpofe, he found that the 
air entered very flowly at the bark of young ftioots 
and branches, but much more freely through old 
bark ; and that in different kinds of trees it had dif- 
ferent degrees of more or lefs free entrance. 
And likewife, that there is fome air both in an elaftic 
and unelaftic ftate, mixed with the earth (which may 
well enter the roots with the nourifhment), he found 
by feveral experiments, which he gives in the before- 
mentioned treatife. 
The excellent Mr. Boyle, in making many experi- 
ments on the air, among other difcoveries found, that 
a good quantity of air was producible from vegetable^, 
by putting Grapes, Plums, Goofberries, Peafe, and 
feveral other forts of fruits and grains into exhaufted 
and unexhaufted receivers, where they continued for 
feveral days emitting great quantities of air. 
This put the curious Dr. Hales upon farther re- 
fearches to find out what proportion of air he could ob~ 
% tain out of the different vegetables, in which it was 
lodged and incorporated, which he performed by di- 
vers chymio-ftatical experiments, which he gives in 
many inftances in his treatife of the analyfis of the air, 
plainly fliewing in what manner he performed them, 
and the events of them. 
That from half a cubic inch, or 135 grains of heart 
of Oak, freflh cut from a growing tree, there were 10S 
cubic inches of air generated, which is a quantity 
equal to 216 times the bulk of the piece of Oak ; that 
the weight of it was above 30 grains, one quarter 
part of the weight of 135 grains. 
And he adds, that he took the like quantity of thin 
ftiavings from the fame piece of Oak, and dried them 
at fome diftance from a gentle fire for 24 hours •, in 
which time they evaporated 44 grains of moifture ; 
which 44 grains dedudled from 135 grains, there re- 
mains 91 grains for the folid part of the Oak: then 30 
grains will be one third of the weight of the folid part 
of the Oak. 
He gives another experiment of Indian Wheat, which 
grew in his own garden, that he took 388 grains of 
it when it was not come to its full maturity, and that 
there were generated from it 270 cubic inches of air; 
the weight of which air was 77 grains, viz. one fourth 
of the weight of the Wheat. 
And again, that a cubic inch, or 3 1 8 grains of Peafe 
generated 396 cubic inches of air, or 113 grains, i. e. 
fomething more than one third of the weight of the 
Peafe. 
And again, that from one ounce, or 437 grains of 
Muftardfeed, 270 cubic inches of air were generated, 
or 77 grains, which is more than one fixth part of the 
ounce weight. 
He likewife adds, that there is a great plenty of air 
incorporated into the fubftance of vegetables, which, 
by the adtion of fermentation, is routed into an elaftic 
ftate, as is evident from thefe experiments following. 
On the 2d day of March, he poured 42 cubic inches 
of ale from the tun, which had been there fet to' fer- 
ment 34 hours before into a bolt head; and from that 
time to the 9th of June, it generated 639 cubic in- 
ches of air, with a very unequal progreflion, more or 
lefs, as the weather was warm, cool, or cold ; and 
fometimes, upon a change from warm to cool, it re- 
forbed air, in all 32 cubic inches. 
From the 2d of March to the 16th of April, 12 cu- 
bic inches of Malaga Raifins, with 1 8 cubic inches of 
water, generated 41 1 cubic inches of air; and then 
again, it reforbed 35 cubic inches in two or three cold 
days.. From the 21ft of April to the 16th of May, 
it generated 78 cubic inches ; after which, the 9th of 
F June, 
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