49 



passed those of Rothamsted, the work was being continued in the 

 friendliest manner, and utterly free from envy and dispute. 



From these memoranda regarding this great meeting of agricultural 

 scientists at Halle, it will be seen that the fixation of atmospheric nitrogen 

 by plants of the sub-order papillionaceae, is now established beyond all 

 possibility of doubt, and that that farmer will be the truest artist and 

 become the richest man who makes the best use of these well established 

 results of scientific investigation in agriculture. 



But although it is a fact that these humble leguminous plants are 

 so highly gifted by nature, it is equally certain that the cereals 

 and other plants of a higher order cannot appropriate nitrogen 

 in this direct way. They and their rootlets must search for it in the 

 soil in the form of nitric acid, which may have been brought from the 

 atmosphere into the soil or have originally existed as nitrogen in its or- 

 ganic matter or humus, or may have been produced by the oxidation of 

 ammonia. Decayed vegetable matter, peat and black muck contain quan- 

 tities }f nitrogen varying from ^ to 2 per cent, in the air dried condition. 

 When this is composted or mixed with other soil and stable yard 

 manure the nitrogen is gradually made available for plant food ; in fact 

 it undergoes a process of oxidation, being first changed into ammonia 

 and then if bases are present into nitric acid. This lecture would 

 certainly be incomplete without some notice of these important com- 

 pounds. We shall now make some reference to ammonia ; later on to 

 nitric acid. 



(Here experiments were introduced illustrative of the great solu- 

 bility and alkaline character of ammoniacal gas ; the formation of 

 ammonium chloride and the oxidation of ammonia in the ignition of the 

 bichromate.) 



But it is our business this evening to go further and ask what use the 

 plant makes of the nitrogen which it appropriates. It is immaterial 

 whether we suppose that the nitrogen is assimilated as such or as 

 ammonia or as nitric acid, in any case the use which is made of it by 

 plants, and the wonderful products into which it is transformed 

 by the vital activities at work in these, are simply miraculous. A very 

 high authority, Mr. Warington, a colleague of Sir Henry Gilbert and Sir 



