ACTION OF L"»=:ATES ON THE ATMOSPHERE. 1?3 



periments of Piiestley and Ingenhousz have been con- 

 firmed, extended in a variety of ways, or explained on 

 the {principles of improved chemistry, by Dr. Percival 

 and Mr. Henry in England, Dr. Woodhouse in Ameri- 

 ca, and M. Sennebier and M. Tl eodore de Saussure, as 

 well as various other philosophers, on the continent of 

 Europe. It is agreed that in the day-time plants imbibe 

 from the atmosphere carbonic acid gas, (which was for- 

 merly called fixed air, and is an union of oxygen and 

 carbon), that they decompose it, absorb the carbon as 

 matter of nourishment which is added to the sap, and 

 emit the oxygen. So they absorb the same gas from 

 water, when it is separated from that fluid by the action 

 of light. The burning of a candle, or the breathing of 

 animals, in confined air, produces so much of this gaSj 

 that neither of these operations can go on beyond a cer- 

 tain time, but the air so contaminated, serves as food for 

 vegetables, whose leaves, assisted by light, soon restore 

 the oxygen, or, in other words, purify the air again. 

 This beautiful discovery, for the main principles of 

 which we are indebted to the celebrated Dr. Pnestley, 

 shows a mutual dependance of the animal and vegetable 

 kingdoms on each other, which had never been suspected 

 before his time. Compar.itive experiments upon the 

 lower tribes of these kingdoms have not yet been made, 

 but they would probably afford us a new test for distin- 

 guishing them. The air so copiously purified by a Con- 

 ferva, one of the most inferior in the scale of plants, 

 may be very extensively useful to the innumerable tribes 

 of animated beings which inhabit the same watere. The 

 abundant air- bubbles which have long ago given even a 



