182 J. H. Gilbert— Points in connection 1 



A few years ago Deherain substantially revived this view. 

 He maintained that at a certain depth the air of the soil is poor 

 in, or destitute of, oxygen; that hydrogen is evolved from the 

 decomposing organic matter; that it unites with free nitrogen 

 to form ammonia; and, tbat so, combined nitrogen increases 

 in the soil in spite of the growth and removal of crops. This 

 view he supports by some laboratory experiments. 



It is obvious tluir if the realitv of this action in soils were 

 unquestionably established, it would greatly aid the solution 

 of the question we are discussing. There, are, indeed, results 

 of others on record which would seem to lend it probability. 



Thus, Bretscbn eider found, on exposure of a mixture of 



humic acid and quartz sand to the air for a whole year, under 



• in winch it was protected from rain and insects, that 



there was a gain of combined nitrogen which would represent 



an increase of more than 40 lbs. per acre. 



Again, Boussingault exposed a moist garden soil for three 

 months, and found a small gain of nitrogen. His explanation, 

 was, however, different. He supposed it possible that ozone 

 might be evolved in the oxidation of organic matter in the 

 BOU, and unite with free nitrogen, and so nitric acid be pro 

 duced, and the soil gain in combined nitrogen. In other ex- 

 periments Boussingault put mixtures of vegetable mould and 

 pure sand in small quantities in large glass vessels which he 

 perfectly closed and preserved in a dark cellar for a whole 

 year. At the end of that period oxidation of organic matter 

 had taken place, nitric acid was found, but there was upon the 

 wholea small loss of combined nitrogen. Lastly in regard to 

 B '"i _ tit's results h irii _ | l;ls already 



been shown that in all of his experiments with plants in which 

 his soils consisted of ig tited brick, or the like, 



without organic matter, he found no gain of combined nitro- 

 gen in soil and plant. In 1858 and 1859, however, he made a 

 number of experiments on growth, in which part of the soil 

 consisted of rich garden mould; and in two cases with lupins 

 growing in confined air, and in one with haricot growing in 

 free air, his results showed a notable gain of combined nitro- 

 gen : and although the quantity of garden mould employed 

 was not the same in the three cases, the gain of nitrogen was 

 approximately in proportion to the amount of soil used". The 

 gain was, indeed, in the soil rather than in the plant. In the 

 other experiments, however, either much less or no gain was 

 indicated. 



Much more recently, Boussingault has published the results 

 of experiments which showed that when a garden soil was con- 

 fined for about eleven years in closed glass vessels in an atmos- 

 phere containing oxygen, the free nitrogen did not serve for 



