l6o On the Injlusnce luh'ich Oxygen has 



would take place if I endeavoured to prevent the catbonici 

 acid gas from being abforbed by the water. 



If water be placed in an atmofphere of pure carbonic acid 

 gas, the water never cbforbs more of fuch gas than what is 

 equal to its volume, provided the fluid fuftains no other pref- 

 fure than that of the weight of the atmofphere. The quan- 

 tity abforbed by the water is lefs, the greater the quantity of 

 the atmofpheric air mixed with the carbonic acid gas. When 

 the carbonic acid gas irtakes only 0"02 of the atmofpheric 

 air, the portion abforbed is not perceptible. This ahforption^ 

 therefore, may be always rendered imperceptible, cither by 

 increafing the volume of atmofpheric air which is in contact 

 with the feeds, or by leaving in the receiver only as much 

 water as is abfolutely necefl'ary for the purpofe of germiua- 



lion. 



Experiment It. 



Eighteen peas were placed in li^ cubic inches of atmo-« 

 fphcric air, purified by lime-water, under a bell clofcd with 

 jijercurj'. The fluid rofe an inch higher than within the 

 veflel. Into this receiver I tranl'mitted i cubic inch of water 

 in which the peas were to germinate: they floated half in 

 it on the mercury. Ten days after, the peas had grown fo 

 much that their roots were from three to four lines in length. 

 I examined the air under the bell, and found that its volume 

 was not fenfibly lefTcned. Lime-water fliowed 0.09 of car- 

 bonic acid, and the phofphoric eudiometer, after deducting 

 the carbonic acid, 0'i2 of oxygen gas, and therefore 0-09 

 lefs than in atmofpheric air. When nitrous gas was mixed 

 in equal parts with this air, there remained a refiduum of 

 132 parts. If we admit, with Lavoifier, that atmofpheric air 

 contains about 0-37 oxygen gas, or 0.06 lefs than is indicated 

 l)y the phofphoric eudiometer, which in the air of my labo- 

 ratory gives only cai oxygen gas, it will be found that the 

 air under the bell, before the peas were introduced, contained' 

 3-105 cubic inches oxygen gas and 8"395 of azotic gas; and 

 that after the germination the fame volume of air contained 

 I'^S cubic inches of oxygen gas, 8*395 of azotic gas, and 

 1'035 of carbonic acid gas; confequently, l"225 cubic inches 

 of ativofpheric oxygen gas v. ere employed to form the bafts 

 8 '^ of 



