J. H. Gilbert— Points in connection wiUi Vegetation. 193 



is, in fact, equal to the total amount that maybe in question as 

 between two subsoils to be compared. Further, if this avail- 

 able nitrogen exist in the subsoil as nitrates, it may be a ques- 

 tion whether there would be a sufficient amount of organic 

 matter present to insure the evolution as ammonia of the nitro- 

 gen of the nitric acid. 



It has been shown, then, that there are many questions still 

 open for investigation in regard to the relations of the surface 

 soil to combined nitrogen ; and there are obviously also equally 

 important points to investigate in regard to the nitrogen of the 

 subsoil, before we can hope to arrive at a satisfactory solution 

 of some of the problems which the consideration of the facts of 

 vegetable production which have been adduced, suggest for 

 enquiry. Nor are the problems still open connected with the 

 am til the condition, of the mineral food of plants within 

 the soil, either lew. or without special, and independent interest. 

 And although those relating to the nitrogen seem to call for 

 the first attention, the marked effects, so tar. of potash manures, 

 in increasing the amount of nitrogen assimilated over a given 

 area by the Leguminosas, seem to indicate the probability that 

 even the difficulties ,-oimected with the sources of the nitrogen 

 of our crops niav not be solved without further knowledge as 

 to the required conditions, or the actions, of the incombustible 



More t.< ' ,-qulred.— Our results in regard 



to the variations in the amount of nitrogen in the soils and sub- 

 soils of our different experimental plots, obtained by the soda- 

 lime process results already referred to, re- 

 lating to the composition of the drainage water from plots 

 variously manured, as well as others of quite a different kind. 

 have shown the absolute necessity for an extended investigation 

 of the soil question by more exact methods ; and Mr. Warmgton 

 is about to devote, probably some years, to this enquiry at 

 -ted. It is proposed that the questions relating to the 

 nitrogen in subsoils should be the tirst considered, since, if the 

 results do throw light upon some of the points at present in 

 doubt, a definite step in advance will be so gamed : and should 

 they not do so, the ground will thus be cleared of certain obvi- 

 ous suppositions, and the course of further research will be the 

 more clearly indicated But if the amount of nitrogen to be 

 itited should prove to be represented by only units in 

 the third decimal place per cent, sav ■nO-2 for example, it is ob- 

 vious that to get as little as lour milligrams involved m the 

 analysis. 200 grams of soil would have to be operated upon. 

 s ..I the problem are thus sufficiently obvious. 

 But, by the aid of the process*-- - -wi.icn 

 have been explained by the President in his opening address, 



