DR. DAUBENY ON THE ROTATION OF CROPS, ETC. 251 



organ, or the same proximate principle belonging to the plant, may admit at all of 

 this change in its constitution taking place ; or if it can, in what degree the presence 

 of this new principle may affect the healthy development of the vegetable. 



By turning to the Table which states the relative quantities of alkaline ingredients 

 extracted from the different soils by water impregnated with carbonic acid, it will be 

 seen, that in most of these the amount of soda predominated over that of potass, and 

 yet the latter alkali was principally found in their ashes, an indication at least of some 

 superior adaptation of potass to soda for the organization of plants*. 



Again, it is remarkable, that whilst in several of the soils soda appeared to 

 exist in the form of a carbonate (since the quantity of chlorine was so small that 

 only a minute trace of it was discoverable in them), in many of the ashes of the 

 plants, only as much soda was detected as would contain sodium equivalent to the 

 chlorine present. 



Hence it would seem to follow, that common salt, when it acts beneficially upon 

 land, does not assist the crop by virtue of the alkali it imparts to it, but in some 

 other way, and that it is still questionable, at least in the case of terrestrial species, 

 whether plants have the power of decomposing chloride of sodium, and of separating 

 its chlorine. 



Lastly, the analyses contained in this paper may be of use at the present moment, 

 by contributing to show, how much still remains to be done, before we can flatter 

 ourselves at having attained any sure knowledge of the normal constitution of plants, 

 and of the range of variation of which under natural circumstances it is susceptible. 

 At a time when certain enlightened members of the Royal Agricultural Society 

 have prevailed upon that great Body, to devote a portion of their funds to the prose- 

 cution of the chemical analysis of the ashes of vegetables, whatever tends to render 

 more palpable the importance of such an investigation, may be of service, in aiding 

 their meritorious efforts, to give a more scientific direction to the inquiries which such 

 associations are intended to promote, and in vindicating the utility of the course 

 which they have in this instance adopted. 



Now the facts and observations detailed in the present paper contribute in two re- 

 spects towards this object, viz. by showing that the composition of the most commonly 

 cultivated plants is still open to much uncertainty ; and 2ndly, by pointing out in 

 what way an exact knowledge of their inorganic ingredients might aid us towards the 

 solution of many important practical questions. 



I hope, it will not be attributed to any blindness on my part to the deficiencies and 

 imperfections which exist in this paper, if I remark, that an investigation of a similar 

 kind to the one herein detailed, if carried out on a more adequate scale, undertaken 

 on ground more carefully selected, conducted with a more vigilant attention to all 

 the minute circumstances which might influence the result, and accompanied by a 



* This is also shown very strikingly in a paper on the analysis of Fuci, read to the British Association at 

 Cambridge, by Mr. Schweitzer, in June 1845, 



MDCCCXLV. 2 L 



