G04 The Luis Weedon Flan of Groicing TVIieat. 



more, th.in 5 per cent, of water separable by further drying at 

 212°. For convenience and uniformity, the determinations in 

 the Table are all given as calculated upon the soil so dried at 

 212° ; though separate portions were always employed for the 

 determination of the moisture in this way, and those of the 

 nitrogen were always made upon the partially and only air-dried 

 substance. 



The nitrogen determinations were made by burning with soda- 

 lime, collecting the ammonia in hydrochloric acid, and estimat- 

 ing as platinum salt in the usual way. It is obvious 'that this 

 method does not give that portion of nitrogen which may exist 

 as nitric acid. But from the interesting results of Professor 

 Way, on the power of soils to absorb ammonia and nitric 

 acid respectively, and on the general relation of these two sub- 

 stances in drainage-water, it may perhaps safely be concluded 

 that, in most ordinary soils, but a very small proportion of their 

 contents of nitrogen will be retained as nitric acid. 



Tlie two, three, or more determinations upon each soil, were 

 in only one or two cases made by the same analyst ; two persons 

 being employed upon the series, each, as a rule, making two 

 determinations upon the same specimen. In this way it was 

 hoped to eliminate any prevailing tendency to high or to low results 

 which might attach to the work of either operator. It is 

 probable it would be the opinion of most chemists, that the 

 discrepancies in the percentage amounts of nitrogen which the 

 Table exhibits, are neither greater nor more numerous than were 

 to be expected in the manipulation of the process employed, by 

 two operators on such a series. When, however, it is remem- 

 bered that, as already pointed out, the large dressing of a hun- 

 dred pounds of nitrogen per acre, distributed through the soil to 

 the depth of 1 foot, would only raise its percentage of nitrogen 

 by 0*0025, equal 4-00'uoth of its weight, it would at once be 

 seen, that the separate determinations on the same soil frequently, 

 nay, generally, differ much more from each other, than would the 

 actual soil before and after such a potent manuring. It is clear 

 then from this simple illustration, that such methods of estimat- 

 ing the nitrogen in soils are quite inapplicable to determine the 

 difference in this respect between a soil yielding 16 bushels of 

 wheat without manure, or twice, or twice and a half the amount, 

 with it. That is to say, such methods are quite incompetent 

 adequately to treat the question of the mere temporary " condi- 

 tion " of soils. 



Exercising then all due caution, on the score both of tlie diffi- 

 culty of fairly and uniformly sampling soils for analysis, and. of 

 that of accurately determining the nitrogen by current methods, 

 let us see wliat are some of the more sreneral indications of the 



