Royal Institution. 223 



traded from the sulphur hy potassium, which took place 

 with vivid combustion, formed an alkali. Mr. Davy en- 

 tered into some general views respecting the manner in 

 which the oxygen of the atmosphere, and that dissolved in 

 water, were renovated. Oxygen is absorbed, and carbonic 

 acid is produced, in the respirations of animals, in combus- 

 tion, and in fermentation ; vegetables in the sunshine ab- 

 sorb carbonic acid and evolve oxygen. Mr. Davy com- 

 bated the idea that this function o\ vegetable hie was not 

 sufficient to supply oxvgen equivalent to that consumed. 

 There is no other mode known in which carbonic acid is 

 decomposed in the processes of nature ; and did not vece- 

 tables absorb it, it must be constantly accumulating; which 

 is known not to be the case. A great part of the solid sur- 

 face of the globe is covered with plants, and light is essen- 

 tial to their healthy growth ; and therefore great quantities 

 of oxygen are produced in countries where there is little 

 animal hfe. Fishes, he stated, will live m confined por- 

 tions of water containmg aquatic plants, and the oxvt^en 

 they absorb is compensated for by the plants, which' de- 

 conipose the carbonic acid afforded in their respiration. 

 This view of the connection of plants and animals in their 

 action upon air, is not only supported by many proofs, but 

 is likewise, says Mr. Davy, conformable to the analojry of 

 nature ; — it proves to u5 that the meanest weed, the niost 

 poisonous plant, is not without its uses in the ceconomy of 

 things — the different parts of the atmosphere are mingled 

 try wmds — -the carbonic acid not consumed by sound plants 

 is carried into the waters, dissolved by rain, mists, and 

 dews — the sea is kept in agitation by waves and tides, and 

 its influence upon the air constantly exerted— the storni 

 and the whirlwmd assist in this beneficent ministration; 

 and the harmony displayed in such diversified combinations 

 offers a SI riking instance df the wisdom and perfection of 

 the arrangements connected with the preservation of life in. 

 the system of the globe. 



The eighrh lecture of Mr. Davy was delivered on Satur- 

 day, March 14 ; it was devoted to the consideration of the 

 nature, properties, combinations, and uses of chlorine, or 

 oxymuriatic gas. Some experiments were also made ou 

 enchlorine, a gas recently discovered bv the Professor. 



'i'he illustrious Scheele discovered chlorine in 1774, and 

 he considered it as an undecompounded body. Soon after 

 Lavoisier and Berthollet regarded it as a compound of mu- 

 riatic acid gas and oxygen, and their views were embraceil 

 by all the chemists in Europe; and during a period of 30 



y cars 



