DR. DAUBENY ON THE ROTATION OP CROPS, ETC. 235 



and containing the following constituents : — 



Silica . 0-472 



Phosphoric acid . . . . r070 



Sulphuric acid . . . . 0*157 



Carbonic acid .... 0*785 



Chloride of sodium . . . 0*130 



Potass 3*300 



Soda 0-055 



Magnesia 0452 



Lime . 0*178 



6-599 



In the case of the next crop, the turnips, I have not sufficient data to determine 

 with exactness the amount of inorganic ingredients extracted from the soil, having 

 omitted to weigh the bulbs, from which the ash, in the case both of the permanent 

 and shifting crops, was derived. 



I find, however, that 1000 parts of a good sample from the neighbourhood of 

 Oxford yielded 3-15 of ash, of which about 0*55 was extraneous, so that 2-6 grains 

 will represent the amount of inorganic constituents really present. 



The bulbs obtained from the permanent crop in ten years amounted to about 

 1008 lbs. ; so that the inorganic constituents extracted from the soil in this instance 

 may be reckoned at about 2*62 lbs. 



Now 2*62 lbs. of inorganic matter would, according to the previous data, consist 



of the following ingredients, viz. 



lbs. 

 Silica 0-075 



Phosphoric acid . . . 0-360 



Sulphuric acid .... 0-310 



Carbonic acid .... 0-2/3 



Chloride of sodium . . 0*050 



Potass 1*110 



Soda 0*000 



Magnesia 0-110 



Lime 0332 



2*620 



The shifting crop of turnips in the same period yielded of bulbs 1765 lbs., which, 

 according to the same calculation, would have produced 458 of real ash. 



For as 1008—262—1765—4-58. 



Now 4-58 lbs. of ash would contain the following proportions of inorganic consti- 

 tuents, viz. 



MDCCCXLV. 2 I 



