142 THE ART OF CULTURE. 



Dutch chemists with chlorine, is exposed in a vessel 

 with chlorine gas to the direct solar rays, chloride 

 of carbon is immediately produced ; but the same 

 compound can be obtained with equal facility in the 

 diffused light of day, a longer time only being re- 

 quired. When this experiment is performed in the 

 way first mentioned, two products only are observed 

 (muriatic acid and perchloride of carbon) ; whilst by 

 the latter method a class of intermediate bodies are 

 produced, in which the quantity of chlorine con- 

 stantly augments, until at last the whole liquid 

 hydrocarburet of chlorine is converted into the same 

 two products as in the first case. Here, also, not 

 the slightest trace of decomposition takes place in 

 the dark. Nitric acid is decomposed in common 

 daylight into oxygen, and peroxide of nitrogen; and 

 chloride of silver becomes black in the diffused light 

 of day, as well as in the direct solar rays; — in 

 short, all actions of a similar kind proceed in the 

 same way in diffused light as well as in the solar 

 light, the only difference consisting in the time in 

 which they are effected. It cannot be otherwise in 

 plants, for the mode of their nutriment is the same 

 in all, and their component substances afford proof 

 that their food has suffered absolutely the same 

 change, whether they grow in the sunshine or in the 

 shade. 



, All the carbonic acid, therefore, which we supply 

 to a plant will undergo a transformation, provided 

 its quantity be not greater than can be decomposed 

 by the leaves. We know, that an excess of carbonic 

 acid kills plants, but we know also that nitrogen to 

 a certain degree is not essential for the decomposi- 

 tion of carbonic acid. All the experiments hitherto 

 instituted prove, that fresh leaves placed in water 

 impregnated with carbonic acid, and exposed to the 

 influence of solar light, emit oxygen gas, whilst the 

 carbonic acid disappears. Now in these experiments 

 no nitrogen is supplied at the same time with the car- 

 bonic acid; hence no other conclusion can be drawn 



