8 34 THE POPULAR SCIENCE MONTHLY. 



show that in all cases the nitrogen first assumes the form of ammonia, 

 and that the latter is, strictly speaking, the only substance capable of 

 beinc nitrified. In the case of urea this has been observed to lead to 

 some interesting results. Thus, if nitrification is induced in a solution 

 of urea containing no salifiable base, the process stops when one half 

 the nitrogen has been oxidized, ammonium nitrate being produced. If 

 the concentration exceeds a certain limit no nitrification occurs, the 

 alkalinity produced when the urea is converted into ammonium car- 

 bonate being sufficient to prevent the action of the ferment. If, how- 

 ever, gypsum be present, the well-known double decomposition into 

 calcium carbonate and ammonium sulphate takes place, and, the latter 

 having a neutral reaction, nitrification proceeds unhindered. 



An interesting and hitherto unexplained fact which was noticed in 

 Warrington's experiments is, that sometimes nitrous and sometimes 

 nitric acid was produced, and at times both in the same solution. The 

 experiments thus far published suggest the possibility of the existence 

 of two ferments, a nitric and a nitrous, but on this branch of the sub- 

 ject we may expect more light when investigations now in progress at 

 Rothamsted are made public. 



Some investigations into the distribution of the nitric ferment in 

 natural soil are summarized by Warrington as follows : " I am dis- 

 posed to conclude that in our clay soils the nitrifying organism is not 

 uniformly distributed much below nine inches from the surface. On 

 much slighter grounds it may perhaps be assumed that the organism 

 is sparsely distributed down to eighteen inches, or, possibly, somewhat 

 farther. At depths of from two feet to eight feet there is no trust- 

 worthy evidence to show that the clay contains the nitrifying organ- 

 ism. It is, however, probable that the organism may occur in the nat- 

 ural channels which penetrate the subsoil at a greater depth than in 

 the solid clay. In the case of sandy soils we may probably assume 

 that the organism will be found at a lower depth than in clays." 







SKETCH OF GENERAL JOHN NEWTON. 



&ENERAL NEWTON has commended himself as one who is en- 

 titled to acknowledgment for useful and distinguished service 

 in two fields. As a member of one of the branches of the military 

 establishment he did active duty as an army engineer and a com- 

 mander of men, acquitting himself with honor on every occasion, dur- 

 ing the whole period of the war of the rebellion. In peaceful times, 

 his career has been within his own preferred field of work, where 

 theoretical knowledge and practical skill in application and execution 

 were equally in demand, and were united in carrying out the impor- 

 tant enterprises that were intrusted to him. In his works as an engi- 



