230 



DR. DAUBENY ON THE ROTATION OF CROPS, ETC. 



Of the Julm, — 100 parts yielded 137 of ash, of which 100 parts contained- 



Charcoal and sand, extraneous 6*22 

 Peroxide of iron, extraneous 1*53 



Ingredients of the aulm 



775 

 90-58, viz.- 



< 



Total 98-33 



Silica .... 

 Phosphoric acid . 

 Sulphuric acid . 

 Carbonic acid . 

 Chloride of sodium 073 

 Soda .... 

 Potass .... 

 Magnesia . . . 

 Lime .... 



98-33 



100-03 



According to these data the crop of barley will consist as follows :- 



Now according to this calculation, 100 parts of the mixed ash ought to contain 

 the subjoined quantities of the ingredients below- mentioned, and by comparing these 

 with the composition given of the ashes obtained from the three crops grown in the 

 Botanic Garden, which I have deduced from the analysis before given, after deducting 

 in each instance the matters regarded as extraneous, it will be seen that there is a 

 near correspondence. 



charcoal, for after the first analysis had been completed, another portion of the ash was fused with potass, after 

 which the silica obtained agreed within 0*2 with that procured in the first instance by the usual process. 



I am the more anxious to state "this, as it will be seen from the statement given in a subsequent page, that 

 there is a great discrepancy between the per-centage of silica given in Mr. Way's analysis and that reported by 

 Sprengel, a discrepancy which, without this explanation, might be attributed to a want of care on his part in 

 not dissolviug the whole of the silica. 



