338 QUARTERLY JOURNAL. 



found. We know, besides, that in certain kinds of plants, potas- 1 



sa may be replaced by soda, and lime by magnesia. 



It results, moreover, from the investigations of M. Boussaingault 



{Annales de Chimie et de Physique, 3** Serie, t. i. p. 242), that on 



an equal surface (4 acres [ID of the same field manured once, 



there will be removed from the soil, by five successive crops : — 



Principles of 



the soil. 



1st year, by a crop of potatoes (tubercles without stalks or leaves) .. 246.8 lb. 



2d " *' wheat (straw and grain) 371.0 " 



3d " " clover 620.0 " 



4th I " wheat* 488.0 " 



^ " peeled turnips.. 108.8 " 



5th " " of oafs (straw and grain) 215.0 •* 



By a crop of beet-rootsf (roots without leaves) 399.5 " 



" peas (seeds and straw) 618.0 •• 



rye , 284.6 » 



*' artichokes (hel. tuberosus) 660.0 ♦* 



Of these numbers which express the quantities of inorganic 

 substances extracted from the same soil by different plants, and 

 extracted or removed consequently in the crop, it results that diffe- 

 rent plants introduce into their organism unequal weights of these 

 principles of the soil. 



The attentive examination of the principles of their ashes 

 shows, moreover, that they differ essentially with respect to their 

 quality. 1000 parts of beet roots, potatoes, or turnips, leave, by 

 cultivation in the dry state, 90 parts of easily fusible ash, contain- 

 ing a great quantity of carbonate of potassa and salts, with alka- 

 line bases. Of these 90 parts, 75 dissolve in cold water. 



2000 parts of dried fern likewise give 90 parts of ash ; but oi 

 these 90 parts, nothing dissolves in water, or only a trace is dis- 

 solved. (Berthier.) 



It is the same with the ash of wheat straw, and those of barley, 

 peas, beans, tobacco, &c. With equal weights to their ash, very 

 unequal quantities of its principles dissolve in water. Some ashes 

 are completely soluble in water ; some are only half soluble in 

 it ; and again others contain only traces of principles soluble in 

 water. 



If we pour an acid — hydrochloric acid, for example — on th€ 

 portions of ashes insoluble in water, we find that with a great 

 number of plants, the residue left by the water is completely so- 

 luble in the acids (beet roots, potatoes, turnips, &,c.) • that with 

 others, only half of these residues are dissolved in the acid, whilst 



• In a second and third assolement. 



t In the quinquennial crop above referred to, \Vheat is mentioned twice. In th« 

 second year, by a crop of wheat, 371 lbs., and in the fourth year, 488 lbs. of inorganic 

 principles were removed from the soil. This dilTerence is owing to the unequal 

 quantity of straw and grain which were collected in these two years. In the one, 

 the combined weight of the straw and grain was 8,7J)0 lbs . ; and in the other, on the 

 contrary, 10,8o8. Tlic relative proportion of these ashes was absolutely the same 

 as these numbers. 



