Miscellaneous. 69 



lution is, whence then comes the excess of azote which the crops 

 contain, and in ^ more general manner, the azote of plants, which 

 the soil has not furnished ? He di\'ides his inquiry' into the three 

 following parts : — 



First. Inquiry into and determination of the proportion of the 

 ammonia contained in the air of the atmosphere. 



Second. Is the azote of the air absorbed by plants? 



Third. Influence on vegetation of ammonia added to the air. 



1. The author remarks that since the observation of M. Theodore 

 de Saussure, that the air is mixed with ammoniacal vapours, three 

 attempts have been made to determine the proportion of ammonia 

 in the air : a million of kilogrammes of the air, according to M. 

 Grayer, contain 0-333 kil. N- H^ ; according to Mr. Kemp 3-880 

 kil. ; according to M. Fresenius, of the air of the day, 0-098 kil., and 

 of night air, 0-169 kil. He states that he has shown the cause of 

 these discrepancies, and proved that the quantity of ammonia con- 

 tained in the air is 22-4r7 grms. for a million of kilogrammes of the 

 air; and that the quantity oscillates between 17-14 grms. and 

 29-43 grms. 



2. The author states that though the azote of the air is absorbed by 

 plants, the ammonia of the air contributes nothing to this absorption. 

 Not that ammonia is not an auxiliary of vegetation, but the air con- 

 tains scarcely 00000000224, and in this proportion its efl^ects are 

 inappreciable. These conclusions are founded upon a great number 

 of experiments in which the plants lived at the expense of the air 

 without deri\ing any thing from the soil. For the present he con- 

 fines himself to laying down these two conclusions : — 1. The azote 

 of the air is absorbed by plants, by the cereals, as by all others. 2. 

 The ammonia of the atmosphere performs no appreciable part in the 

 life of plants, when vegetation takes place in a limited atmosphere. 

 After describing the apparatus by means of which he carried on his 

 experiments on the vegetation of plants placed in a soil deprived of 

 organic matter, and the manner in which the experiments were con- 

 ducted, he adduces the results of these experiments in proof of the 

 above conclusions. 



3. With reference to the influence of ammonia on vegetation, the 

 author states that, if ammonia be added to the air, vegetation be- 

 comes remarkably active. In the proportion of 4 ten-thousandths 

 the influence of this gas shows itself at the end of eight or ten days, 

 and from this time it manifests itself with a continually increasing 

 intensity. The leaves, which at first were of a pale-green, assume 

 a deeper and deeper tint, and for a time become almost black ; their 

 petals are long and upright, and their surface wide and shining. In 

 short, when vegetation has arrived at its proper period the crop is 

 found far beyond that of the same plants grown in pure air ; and, 

 weight for weight, they contain twice as much azote. Besides these 

 general eflfects there are others which are more variable, which de- 

 pend upon particular conditions, but which are equally worthy of 

 interest. In fact, by means of ammonia we can not only stimulate 



