EXPLANATION OF THE FAILURE OF CLOVES. 163 



than any oilier of the potash salts. It is also difficult 

 to understand why liquid manure was not employed, 

 and why chloride of sodium was excluded from the list 

 of manuring agents. If we consider what Messrs. 

 Lawes and Gilbert omitted to do in their endeavour to 

 solve the problem, and what they ought to have done, 

 the conclusion is inevitable, that they had no accurate 

 notion of the nature of their task. 



JSTow, the want of a proper insight into the nature 

 of a phenomenon which is to be investigated is surely 

 the greatest of all difficulties in the way of attaining a 

 practical result. If the unproductiveness of a field for 

 clover and peas depends upon a want of nitrogenous 

 food in the deeper layers of the soil, and upon no other 

 cause, the absorptive power of the various soils for am- 

 monia renders it extremely difficult to enrich the sub- 

 soil with this element of food. But the case is quite 

 different with the nitrates, which penetrate to any 

 depth, as the nitric acid is not absorbed by the soil ; 

 probably, nitrate of soda may afford a means of making 

 a field productive for clover or peas, in cases where 

 there is a deficiency of nitrogenous food. 



As manuring with burnt lime is often found bene- 

 ficial for clover and also for peas, and a calcareous soil 

 tends, in a special degree, to promote the formation of 

 nitric acid, it is not improbable that it is owing to this 

 property that lime promotes the growth of deep-rooting 

 plants by converting ammonia into nitric acid, and 

 causing nitrogenous food to find its way to the deeper 

 layers of the soil. 



