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



To determine this, it seemed necessary to appreciate, if possible, first, what mate- 

 rials the soil might have contained, both before the experiments commenced, and 

 after their termination ; and secondly, what might be the constitution of the plants 

 themselves both in the permanent and the shifting crop, as compared with the normal 

 condition of the same. 



But as the experiments which I had instituted extended to no less than sixteen 

 different species, my object being to select at least one out of each natural family, 

 which contained amongst the plants included under it any of those usually cultivated 

 for farm or garden purposes in this country, it seemed necessary to limit that part of 

 the inquiry which involved the necessity of ash analysis to a portion only of the 

 series, and accordingly, in the autumn of 1844, I selected from the crops grown in 

 that year the following as the subjects of chemical examination, namely. Barley, 

 Potatoes, Turnips, Flax, Hemp, and Beans. 



Of each of these six plants, the shifting and permanent crops, after having been 

 weighed in the usual manner, in order to estimate their relative amount, were reduced 

 to ashes, so that the proportion of inorganic to organic matter might in the first 

 instance be determined. 



In consequence of the largeness of the bulk, iron vessels were necessarily employed 

 for burning away the volatilizable parts, and hence a portion of peroxide of iron was 

 always introduced into the ashes, which, being indefinite in quantity, rendered it 

 necessary for me, in the subsequent analyses, to regard the whole of that ingredient 

 as extraneous, and to reject it from the calculation. The same course was also pur- 

 sued with respect to a certain variable amount of sand and charcoal always present 

 in the ash, the former derived evidently from the soil, the latter from the carbo- 

 naceous matter of the vegetable, which could not be entirely removed by the 

 combustion. 



Of each of these six plants it appeared necessary to analyse at least three speci- 

 mens — the first taken from the permanent crop, the second from the shifting one, 

 the third from a piece of ground, not belonging to the spot at wiiich the experiments 

 were carried on, and under ordinary treatment, but corresponding as nearly as pos- 

 sible in natural character to the soil of the experimental garden. 



Thus this part alone of the inquiry involved at least eighteen distinct analyses, an 

 amount of labour, which, as I soon found, my other occupations precluded me from 

 undertaking, and which I was glad to delegate to other hands. 



I therefore esteemed myself fortunate in being able to secure the services of 

 Mr.THOMAS Way, a gentleman, who had for the last two years officiated as Assistant 

 to Professor Graham of University College, London, and who was recommended to 

 me by that distinguished chemist as well-qualified for the task. 



On him, therefore, the merit, as well as the responsibility, of this part of the inquiry 

 must mainly devolve ; all that I can lay claim to in this part of the subject as my 

 own, is the having considered, in conjunction with him, the method of analysis which 



