quantity of water was daily supplied to the grass by 

 means of the stop-cock.* Every day likewise a certain 

 quantity of water was removed by a siphon, and water 

 staturated with carbonic acid gas supplied in its place ; 

 so that it may be presumed, that a small quantity of 

 carbonic acid gas was constantly present in the re- 

 ceiver. On the 7th of July, ^807, the first day of 

 the experiment, the weather was cloudy in the morn- 

 ing^but fine in the afternoon ; the thermometer at 

 C7, the barometer 30.2 : towards the evening of this 

 day a slight increase of the gas was perceived, the next 

 three days were bright ; but in the morning of the 

 1 1 th the sky was clouded ; a considerable increase of 

 the volume of the gas was now observed : the 1 2th 

 was cloudy, with gleams of sunshine ; there was still 

 an increase, but less than in the bright days ; the 1 3th 

 was bright. About nine o'clock A.M. on the 14th 

 the receiver was quite full ; and considering the ori- 

 ginal quantity in the jar, it must have been increased 

 by at least 30 cubical inches of elastic fluid : at timet* 

 during this day globules of gas escaped. At ten on 

 the morning of the 15th, I examined a portion of the 

 gass ; it contained less than _'_ of carbonic acid gas : 

 100 parts of it exposed to the impregnated solution 

 left only 75 parts ; so that the air was four per cent, 

 purer than -the air of the atmosphere. 



I shall detail another similar experiment made 

 with equally decisive results. A shoot from a vine,, 

 having three healthy leaves belonging to it, attached 



See Fig. 17. 



D 9. 



