41 



it ; and at the end of the third day, it had under- 

 gone no variation. At this period, the barometer 

 was 29.75, and the thermometer 68. 



33. In order to examine the air, the saucer and 

 jar were now immersed in the pneumatic trough, 

 and water being admitted into the jar, the mercury 

 fell, and the cup with its solution was withdrawn 

 through the water : the solution effervesced briskly 

 on the addition of diluted sulphuric acid. A portion 

 of the residual air being then transferred into a small 

 jar, was found to extinguish a lighted taper that 

 was plunged in it : and another portion was shaken 

 with lime-water without producing or suffering any 

 change ; neither did it afterwards experience any 

 perceptible loss by agitation with the liquid sulphur- 

 et of potassa, nor by being placed in contact with a 

 stick of phosphorus. The result, therefore, of this 

 analysis teaches us, that, during the growth of die 

 plants, the oxygenous portion of the air gradually 

 and completely disappeared ; and that the carbonic 

 acid that was formed was entirely attracted by the 

 water of potassa employed. 



34. In the process of germination it has been 

 shewn, that the bulk of carbonic acid produced, bears 

 a constant proportion (7, 8.) to that of the oxygen 

 gas which disappears : and to ascertain whether the 

 same did not hold in vegetation, a similar method 

 was adopted. After the foregoing analysis of the 

 air was completed, the jar was allowed to run dry, 

 and being then re-inverted, it was set on its bottom : 

 and the plants, together with the glass-cup, and a 

 bulk of water equal to the solution, were re-placed 

 in it. Water, to the quantity of 25.4 cubic inches., 



