I. AGRICULTURE AND RURAL ECONOMY. 341 



plays an important part in the economy of plant- growth. 

 When seeds germinate on wet blotting-paper, a brown zone, 

 having the reactions of humus, forms at some distance from 

 the seed. The author concludes that humus is produced in 

 this case from a soluble colorless body by the action of the 

 atmosphere. 21 A, Atcgiist, 1871, 748. 



NITROUS AND NITRIC ACIDS IN SOILS. 



Investigations have lately been prosecuted by Chabrier 

 upon the presence and functions of nitrous acids in soils. 

 The soils examined were finely powdered and passed through 

 a sieve, and then bleached, according to the method adopted 

 in the saltpetre works of Algiers, for the purpose of deter- 

 mining the percentage of nitrous and nitric acids. As the 

 result, it was ascertained that all tilled soils contained nitrous 

 acid. Nitric acid, as is well known, is accumulated, especially 

 in dry weather, in the superficial strata of the earth, the re- 

 verse being the case with the nitrous acid. Hence it would 

 seem that the soluble nitrates ascend in the soil by capillarity 

 in dry weather, when they are transformed, at least in part, 

 into nitrates, which, on the other hand, are washed out by 

 the rain. The water of the soil generally contains 1 part of 

 nitrous acid to 25,000 parts of water; never more than 1 part 

 in 5000. Fields which have lain fallow contain little nitrous 

 acid but much nitric acid; while, on the other hand, forest 

 land contains moderate quantities of nitrous and but little 

 nitric acid ; and inundated clay no nitrous and but little ni- 

 tric acid. The author is of the opinion that the nitric acid, 

 in spite of its slight percentage, is of importance in the earlier 

 periods of vegetation. 



DISPOSAL OF THE NITROGEN OF MANURE. 



From more than twenty years of experiment, Laws and 

 Gilbert have ascertained that harvest plants do not by any 

 means take up all the nitrogen which has been put into the 

 soil in the form of manure, or of ammonia, or other concen- 

 trated substances. Even if land be manured with the same 

 amount of nitrogenous matters, and the same plants be culti- 

 vated, not half of the nitrogen is abstracted from the manure. 

 Of the remainder, a certain part is to be met with in the form 

 of ammonia in the drainage water, and a considerably larger 



