62 HOW CROPS FEED. 



Boussingault found in the first tenth of a slow-falling 

 rain (24th Sept., 1853) 66 parts of ammonia, in the last 

 three-tenths but 13 parts, to 10 million of water. In dew 

 he found 40 to 62; in fog, 25 to 72 ; and in one extraordi- 

 nary instance 497 parts in ten million. 



Boussingault found that the average proportion of am- 

 monia in the atmosplieric waters (dew and fogs included) 

 which he was able to collect at Liebfrauenborg (near Stras- 

 burg, PVance) from the 26th of May to the 8th of Nov. 

 1853, was 6 parts in 10 million {Agyonomie, etc., T. II, 

 238). Knop found in the rains, snow, and hail, that fell at 

 Moeckern, near Leipzig, from April 18th to Jan. 15th, 

 1860, an average of 14 parts in 10 million. ( Versuchs- 

 Statlonen, Vol. 3, p. 120.) 



Pincus and Rollig obtained from the atmospheric wa- 

 ters collected at Insterburg, North Prussia, during the 12 

 months ending with March, 1865, in 26 analyses, an average 

 of 7 parts of ammonia in 10 million of water. The average 

 for the next following 12 months was 9 parts in 10 million. 



Bretschneider found in the atmospheric waters collected 

 by him at Ida-Marienhiitte, in Silesia, from April, 1865, to 

 April, 1866, as the average of 9 estimations, 30 parts of 

 ammonia in 10 million of water. In the next year the 

 quantity was 23 parts in 10 million. 



In 10 million parts of rain-water, etc., collected at the 

 following places in Prussia, were contained of ammonia — 

 at Regenwalde, in 1865, 24; in 1867, 28; at Dahme, in 

 1865,17; at Kuschen, in 1865,5^; and in 1866, 7^ parts. 

 {Preus. Ann. d. Layidwirthschaft, 1867.) The monthly 

 averages fluctuated without regularity, but mostly within 

 narrow limits. Occasionally they fell to 2 or 3 parts, once 

 to nothing, and rose to 35 or 40, and once to 144 parts in 

 10 million. 



Quantity of Ammonia per Acre Brought Down by Rain, 

 etc. — In 1855 and '56, Messrs. Lawes & Gilbert, at Roth- 

 amstead, England, collected on a large rain-gauge having 



