260 APPENDIX TO PART I. < 



from E. Phinney, Esq., of Lexington, well known as one 

 of the most skilful agriculturists, "On the reclaiming of peat 

 bogs and the employment of peat as manure." 



SOURCE OF THE CARBON OF PLANTS. (fROM DAUBENY's 

 LECTURES ON AGRICULTURE, 1841.) 



(See Chapter II.) 



** Until within the last century, it would have been taken 

 for granted, that the soil was the source from whence pro- 

 ceeded all the solid matter at least which entered into the 

 constitution of a plant, and there were several circumstan- 

 ces which tended to countenance such an opinion. No 

 plants, it was observed, would continue long to thrive in 

 earth unmixed with some proportion of vegetable mould, 

 and the fertility of the latter is greatly enhanced by the 

 addition of animal or vegetable matter, in that state of de- 

 cay, in which it becomes soluble in water, and therefore 

 fitted to obtain admission into the vessels of plants. 



"Hence, when Priestley had demonstrated, that leaves 

 decompose the carbonic acid of the atmosphere, giving out 

 its oxygen and assimilating its carbon, the doctrine alluded 

 to still to a certain extent maintained its ground; and it was 

 even questioned by Ellis and others, whether in fact, if we 

 were to strike the balance between the opposite influence 

 of a plant during the day and the night, as much carbonic 

 acid might not be exhaled by it at one period, as had been 

 decomposed at another. 



*' I was therefore induced myself to undertake some ex- 

 periments,* the results of which appear to establish, that 

 plants, even in a confined atmosphere, do in reality add a 

 great deal more oxygen to the air than they abstract from 

 it, whilst the amount of carbonic acid which may be intro- 

 duced undergoes at the same time a corresponding dimi- 

 nution. 



" This effect I even found to take place in diffused light, 

 as well as under the direct influence of the solar rays, and 

 to be no less common in aquatic than in terrestrial plants. 



" I also showed, that when a branch loaded with flowers, 

 as well as with leaves, was introduced into a jar containing 



<( * 



See Philosophical Transactions for 1836." 



