THEORIES CONCERNING SOIL FERTILITY 309 



then a field of 40,000 square feet must receive annually upwards of 80 Ib. of 

 ammonia, or 65 Ib. of nitrogen; for, by the observations of Schubler, which 

 were formerly alluded to, about 700,000 Ib. of rain fall over this surface in four 

 months, and consequently the annual fall must be 2,500,000 Ib. This is much 

 more nitrogen than is contained in the form of vegetable albumen and gluten, 

 in 2650 Ib. of wood, 2800 Ib. of hay, or 200 cwt. of beet root, which are the 

 yearly produce of such a field, but it is less than the straw, roots, and grain of 

 corn which might grow on the same surface, would contain. 



"Experiments, made in this laboratory (Giessen) with the greatest care and 

 exactness, have placed the presence of ammonia in rain water beyond all 

 doubt. It has hitherto escaped observation, because no person thought of 

 searching for it. 1 All the rain water employed in this inquiry was collected 

 600 paces southwest of Giessen, whilst the wind was blowing in the direction of 

 the town. When several hundred pounds of it were distilled in a copper still, 

 and the first two or three pounds evaporated with the addition of a little muriatic 

 acid, HC1, a very distinct crystallization of sal-ammoniac (NH 4 C1) was ob- 

 tained : the crystals had always a brown or yellow color. 



"Ammonia may likewise be always detected in snow water. Crystals of 

 sal-ammoniac were obtained by evaporating in a vessel with muriatic acid 

 several pounds of snow, which were gathered from the surface of the ground in 

 March, when the snow had a depth of 10 inches. Ammonia was set free from 

 these crystals by the addition of hydrate of lime. The inferior layers of snow, 

 which rested upon the ground, contained a quantity decidedly greater than 

 those which formed the surface. 



"It is worthy of observation, that the ammonia contained in rain and snow 

 water possesses an offensive smell of perspiration and animal excrements, 

 a fact which leaves no doubt respecting its origin. . . ." 



"We find this nitrogen in the atmosphere, in rain water, and in all kinds of 

 soils, in the form of ammonia, as a product of the decay and putrefaction of pre- 

 ceding generations of animals and vegetables. We find, likewise, that the pro- 

 portion of azotized matters in plants is augmented by giving them a larger 

 supply of ammonia conveyed in the form of animal manure. 



"No conclusion can then have a better foundation than this, that it is the 

 ammonia of the atmosphere which furnishes nitrogen to plants." 



As an average of 15 years, the total amount of nitrogen brought 

 to earth in rain and snow was found to be 3.97 pounds per acre per 

 annum, at Rothamsted. Other records, varying from 3 to 7 years, 

 have shown 3.45 pounds per acre per annum on the Barbados 

 Islands, 3.54 pounds in British Guiana, 3.69 pounds in Kansas, 

 5.42 pounds in Utah, and 3.64 pounds in Mississippi; while the 

 records from Paris show 8.93 pounds, and those from Gembloux, 



1 " It has been discovered by Mr. Hayes in the rain water in Vermont." W. 



