The Lois JVecdon Plan of Groioing TVJieat. 613 



mineral constituents of our crops. It is not, however, all which 

 possess these physical or chemical powers of surface, and these in- 

 herent mineral riches, that will allow, with equal ease, the expo- 

 sure of an equal surface for the development and available 

 activity of these powers and stores. 



That the nitrogen shown to exist in soils by the methods of ana- 

 lysis which have generally ])een adopted, does not necessarily so 

 exist in a form readily and within a limited period assimilable by 

 plants, is easily demonstrable. Thus, with a view to this point, 

 several of the soils which have been the subject of this paper were 

 operated upon as follows. A given weight (100 grains) was put 

 into a flask, 20 ounces of water added, and a little strong caustic 

 potash ley. The flask was then connected by a tube with a 

 Liiebig's condenser, and heat applied so as to keep the mixture 

 gently boiling. A series of smaller flasks, gauged and marked 

 to hold exactly 4 ounces each, were then successively attached as 

 receivers, until tliree separate fifths of the original bulk of fluid 

 had been collected. It has been shown by Boussingault, that 

 when very dilute solutions of ammonia or ammoniacal salt are 

 distilled in this way, practically the whole of the ammonia will 

 come over in the first two-fifths of the distillate. And it is 

 obvious that boiling a soil in a fine state of division with dilute 

 caustic potash for two or three hours, would liberate a very much 

 larger proportion of its nitrogen in the form of ammonia than 

 could be rendered soluble and available for plants in many years 

 of the influence of air and moisture upon a soil in the very 

 limited state of division in which it exists in cultivated land. 

 Collecting, however, a distillate of three separate fifths, super- 

 saturating each with a known quantity of a test acid, adding 

 litmus, and then neutralising liy a test alkaline solution, it was 

 found that only a small proportion of the nitrogen existing in the 

 soil (the quantity varving slightly with the rapidity of the distilla- 

 tion) was obtained in the distillates. And quite conformably with 

 the point established bv Boussingault, and confirmed in our 

 own experiments in the case of rain-waters, the first fifth con- 

 tained by far the larger proportion of the whole ammoni.a which 

 came over ; the third fiftli, in fact, containing very little. It 

 ■was, however, found, that a very much larger proportion of the 

 total nitrogen distilled over as ammonia from tlie soils after they 

 had been sul)mitted to ammoniacal vapours as above described, 

 than bwlore they had been so treated. 



Although, therefore, it may generally happen that a soil which 

 contains the highest per cent, of nitrogen may have a greater 

 aptitude, if well worked, both to acquire more and to yield up its 

 accumulated stores, and hence, so far be more fertile, yet it is ob- 

 viously quite inadmissible to suppose, that the addition of a com- 



