15 



any, in the condition of the remaining nitrogen of the 

 subsoils, according to the comparative history of the 

 plots ; and so enable a judgment to be formed, of the 

 degree in which the organic nitrogen has already been 

 attacked and has yielded up nitrogen in an available 

 form. It may be that any such method as here sup- 

 posed, may involve the action of nitrifying, or of other 

 organisms, of solvents, such as acids, and especially 

 organic acids, perhaps determining the character and 

 composition of the matters dissolved, or some quite 

 different method may be indicated, or the difference in 

 the relation of the carbon to the nitrogen, may be found 

 to have significance. But whatever line investigation 

 of the point may indicate, the desideratum is, in defect 

 of trustworthy evidence on the point derived from the 

 determination of the total nitrogen of the subsoils, to 

 determine by some other means, as between plot and 

 plot of known history, or as between the same plot at 

 different periods of its history, whether, and as far as 

 possible in what degree comparatively, the subsoil 

 nitrogen has been subject to loss, or it may be in some 

 cases to gain. It is obviously of interest, too, to 

 endeavour to get a clue to the changes that take place 

 in the mineral composition of the subsoils also. 



These points may prove to be of importance so far as 

 the subsoils of the plots which have grown wheat, or 

 other cereals, for many years in succession, are con- 

 cerned, and especially in the case of those where such 

 crops have been so grown without any nitrogenous 

 manure. But such lines of enquiry, if at all successful, 

 promise much more fruitful results in the case of soils 

 where other crops, and especially where crops of the 

 Leguminous family have grown ; whilst those relating 

 to Gramineous crop soils will probably be chiefly of 

 interest in contrast or comparison with those relating to 

 the soils where crops of other families have grown. 



At any rate it is essential to bear in mind, that there 

 is nowhere else, such soil and crop history, as at 

 Eothamsted ; and that the collection and preservation 

 of samples of the experimental soils, subsoils, and crops, 



