RUST, SMUT, ETC. 119 



collected in the rain guage of the observatory at Paris. He 

 found that in one year 10. 74 Ibs. of ammonia fell with the rain, 

 and 10.7 Ibs. of nitric acid. In July he found the amount of 

 the ammonia to be the greatest ; in September, the amount of 

 nitric acid to be the greatest. The ammonia was least in March, 

 and increased gradually to July. In August it diminished sud- 

 denly, and continued to diminish until October, attaining its 

 second maximum in February. 



213. These observations, although very interesting, are not 

 satisfactory, because they were made in the neighborhood of a 

 great city. Hence we find that Boussingault discovered much 

 less ammonia in the air far away from towns a gallon of rain 

 water containing only one twenty-fifth of a grain of ammonia. 

 As a general fact, however, the water collected during fogs was 

 extraordinarily rich in ammonia, containing on an average one- 

 third of a grain to kie gallon but an instance has been known 

 before referred to of a gallon of water from a fog containing 

 not less than four grains of ammonia. The constant presenc 3 of 

 this substance in the atmosphere is not only now fully established, 

 but its influence upon vegetable growth in this gaseous form is 

 of the highest interest, and possibly, of the highest importance. 

 214. The experiments of M. Ville upon the effects of ammonia 

 in air upon vegetation, show how rapidly and remarkably its in- 

 fluence is felt. If ammonia be artificially introduced into air in 

 the same proportional average as carbonic acid is found to be 

 constantly present, namely, about one part in 2500 parts of air, 

 its influence soon shows itself upon the leaves, which continually 

 acquire a deeper and deeper tint. The presence of such am- 

 moniacal vapours not only stimulates vegetation, but changes the 

 growth of the plant, and causes the developement and enlarge- 

 ment of particular organs. In prosecuting a series of experi- 

 ments on the phenomena of vegetation, with a view to ascertain 



