DR. DAUBENY ON THE ROTATION OF CROPS, ETC. 223 



The straw of the barley grown on the coast of Wales was not examined, but the 

 ash of the grain from that quarter was found to contain, in 100 parts, 9*64 of potass, 

 1'32 of chloride of sodium, and only 0*84 of soda, the smaller proportion of potass 

 being explained by the larger amount of extraneous matter present in the residuum 

 left by it after calcination, than by the samples previously noticed. 



The small proportion of soda, however, both in this, and in the former case in 

 which the sample was obtained from the neighbourhood of the sea, seems to militate 

 against the general conclusion deduced by Will, from his analysis of barley taken 

 from the interior of Germany, as compared with the same brought from the Nether- 

 lands. 



Potatoes. 



The crop grown in a recently manured portion of the Botanic Garden, separate 

 from the spot set apart for the experiments, proving defective in quality, I selected 

 as my standard a good mealy sort reared in the neighbourhood of Oxford, in the 

 same kind of subsoil. The following will give the relative composition of this, and 

 of the two crops obtained from the ground left for ten years unmanured, which, in 

 the case of that styled the permanent, had borne potatoes for ten years consecutively, 

 whilst in that styled the shifting, it had only borne them in 1844, having been occu- 

 pied with the following plants on the nine years preceding, viz. — 



1835. Delphinium consolida. 



1836. Trifolium pratense. 



1837. Nicotiana rustica. 



1838. Valeriana Phu. 



1839. Valeriana Phu. 



1840. Linum usitatissimum. 



1841. Solanum tuberosum. 



1842. Papaver somniferum. 



1843. Hordeum sativum. 



Standard Crop. 



r 7"6 of ashes. 

 Of the tubers, 1 000 grains yielded about . . . < 755-0 of water. 



L 236*4 solid organic matter. 



1000-0 

 Overlooking the small amount of extraneous matter intermixed, the ash will of course 

 represent the proportion which its inorganic constituents bear to the whole quantity. 

 Now 100 grains of this ash consisted of — 



Sand and charcoal, extraneous . . . 593 

 Peroxide of iron, extraneous . . . . 685 



12-78 



Silica 5-81 



Phosphoric acid 9-68 



Sulphuric acid 5*23 



Carbonic acid 5*84 



Chloride of sodium 2-06 



Chloride of potassium ^'Q7 



Potass 37-99 



Magnesia . 10-98 



Lime ............ 2-71 



99-75 

 12-78 



Real ingredients .... 86-97 



