102 REVIEWS. 



of growth, size and number of leaves, weight of the pro- 

 duct, etc. : — 



No. 1 made of new vegetable matter . . . 0.397 grams. 

 No. 2 " " "... 0.720 " 



No. 3 " " "... 1.130 '' 



No. 4 " " "... 3.280 " 



In No. 2 so little as three milligrams of assimilable nitrogen 

 introduced into the soil enabled the plant to double the 

 amount of organic matter. The proportion of the weight of 

 the seeds to that of the plant formed was in 



No. 1, as 1 : 4.6 grams. 



No. 2, as 1 : 7.6 



No. 3, as 1 : 11.3 



No. 4, as 1 : 30.8 



In no case did the nitrogen acquired by the plant exceed 

 that of the nitrate added to the soil. 



In the experiments where no nitrate was added to the soil 

 the two or three milligrams of nitrogen acquired by the plants 

 during three months of vegetation came in all probability from 

 ammoniacal vapors and nitrates existing or formed in the at- 

 mosphere. To establish their presence, Boussingault arranged 

 an apparatus which detected the production of some nitrates. 

 And, in exposing to the air 500 grams of calcined sand, which 

 had 10 grams of oxalic acid mixed with it, in a glass vessel 

 with an open surface equal to that of one of the flower-pots 

 used in the above experiments, the sand took 0.0013 grams of 

 nitrogen from the air, of which a part was certainly ammonia. 



The object of the researches of which a summary is given 

 in the second paper was, to determine the quantity of nitrates 

 contained, at a given moment, in one hectare of cultivated 

 ground, one of meadow, one of the forest soil, and in one metre 

 of river or spring water. The quantity in the soil was of course 

 found to vary extremely with the extremes of wet or dry 

 weather. Garden soil, highly manured every autumn, con- 

 tained on the 9th of August, 1856, after fourteen dry and 

 warm days, 316.5 grams of nitre in a cubic litre of soil. On 

 the 29th of the month, after twenty rainy days, the same quan- 



