On Vegelat'ion, 321 



cagement of oxygen, during tlic presence of the light, and 

 the change of the same into carbonic acid in the dark, we 

 must allow there will be, between these gases, a certain 

 ratio dependintr on the longer or shorter duration of their 

 exposure to those extremes ; consequently there will be, 

 cceferis paribus, less oxygen and more carbonic acid given 

 out in winter than in summer. 



Carbon is susceptible of solution or suspension in water, 

 as is evident from the coaly residue obtained on evaporating 

 the drainings of dunghills. Carbon is also in a soluble 

 state in all \'egetable mould, as is shown by the brown 

 tinge of a cokHnfusion of any fertile soil. Wherever lieaps 

 of dung are thrown, and water in the interim fallen, there 

 subsequent vegetation is more vigorous ; and so it ever will 

 be where carbon is in a state of solubility by water. The^ 

 infusions of long and of spit, or perfectly rotted dung, are of 

 different hues, the former being but pale, as weakly charged 

 •with carbon. On applying them as manure, the spot fed 

 with the latter produced the first year larger and more vi- 

 gorous plants than the former ; but in the second year 

 (neither parcel being fresh manured) the part supplied 

 with the long dung showed much the superiority ; and so 

 likewise in the third year this latter had somew^hat the 

 advantage : proving that, in the long dung, less of the 

 carbon was (when "first applied) in a state to be taken up 

 by water than in the short and wholly putrificd dung. The 

 latter, therefore, gives out its coaly principle the first year, 

 whereas the former requires more time for its carbon to be 

 rendered in the state proper to be taken up by the plant. 

 Nothing can better illustrate this than the effects of chips 

 of wood as a manure. These having lain some time heaped 

 up, so as to experience a beginning fermentation, were 

 laid upon a portion of land : during the first and second 

 years the earth so manured presented no better produce 

 than other in its vicinity not manured. In the third year 

 the production was more abundant. In the fourth yet 

 more. In the fifth it appeared to have attained its maxi- 

 mum of production, and diminished till the ninth, in which 

 the manure seemed wholly exhausted. In a word, all cir- 

 cumstances the same, vegetation is most strong and vigor- 

 ous where the soil contains the greatest quantity of carbon 

 in a state of solution. Yet, without doubt, there is a cer- 

 tain maximum with regard to the quantum required, beyond 

 which the presence of superabundant carbon will prove 

 unnecessary and expensive, but this proportion must in 

 Vol. XVII. No. 68. X every 



