Vegetable Kingdom on the Animal Creation. 429 ; 
been able to obtain {uch. fine air from this vegetable in the 
iummer* ; the reafon of which 1 will explain elfewhere. 
Theory of exp A. Boiled water, having loft its air, is- verv much 
difpofed to imbibe it from ail bodies which contain this fluid ; 
and, therefore, during the fir ft day or two of its expofure to the 
fun-fbine with the vegetable, this water abforbed all the air 
which the plant emitted ; and even that which had remained 
entangled between the fibres of the vegetable when it was im- 
merfed in this water. The water being at laft faturated with 
this air could take up no more;, and therefore, whatever air, 
alter this faturation, came forth from tire vegetable rofe to 
the top ot the vefleL The quantity of this dephlogifticated 
air was final ler than that which an equaL bulk of the fame 
plant commonly yields, in frefti pump water,, becaufe a great 
deal of air was at firft taken in or abforbed by the boiled water ; 
which abforption does not happen, or at leaft is not fo great., , 
* By continuing to make experiments, during the whole winter, in the hot- 
houles ol the botanical garden, I found that the conferva rivularis yielded deplilo— 
gilficated air of a much luperior quality to that I had ever been able to get from it 
in the fummer, in the open- air; whereas thofe plant?, filch as- the agave 
Americana, c a this triangularis, &c. which yielded in the iummer the bell: air, 
did icarce yield any in the winter (and. that of a quality fcarce better 
than common air) though placed next to the conferva. The quantity of 
dephlogillicated air I got in the winter from the conferva was fo great, that as 
much of this vegetable as occupies about the fpace of one cubic inch com- 
monly yielded from 12 to 16 cubic inches of this air in the fpace of three or four 
days, when the lun did fnine, the quantity, of pump-water being about 160 cubic 
inches. The green matter which Dr. i>riesTley mentions as fpontancoutly 
produced from pump-water, gave in the winter alfo a tolerable quantity of dephlo- 
gilticated air, of a good quality, though not fo fine, or in fnch large quantities, as 
it is ufed to give in the fummer. It feems to be a general rule, that the greater 
the quantity of air obtained fro n vegetables in the fun is, the better is its degree 
of goodnefs. 
when, 
