AGRICULTURAL TEXT-BOOK. 



of rain water ; and from these examinations we find that if we 

 take the annual depth of rain to be about 24 inches, this quan 

 tity conveys to every acre of land the following substances t 

 Nitrogen, . _ 451 jj^ 



Nitric acid, - - - . 103&quot; 



Ammonia, . . 19A- &quot; 



Chlorine, - 12^-&quot; 



Lime, - - 35 



Magnesia, - - 11 &quot; 



227 fte. 



30. Thence it appears that the quantity of ammonia held in 

 the air varies according to the locality; and, probably, other ei*- 

 oumstances. 



31. Horsford, in continuing the experiments above referred 

 to, found that at Boston, in the summer, when vegetable and 

 animal decay is most rapid, the quantity of ammonia in the air 

 k at a maximum, and afterwards decreases regularly until the 

 winter season, when it is at a minimum. The following table 

 shows the amount of thirteen different analyses : 



Date. Ammonia in 1,000,000 



parts, by weight of aur. 



! July 3, - - 42.9995 



2. July 9, - . 46.1246 



3 - July 9, - 47.6308 



4. September 1 to 20, - 29.7457 



5. October 11, - 28.2396 



6. October 14, . 25.7919 



7. October 30, - - 13.9315 



8. November 6, 8.0953 



9. November 18, 12 and 13, 8.0953 



10. November 14, 15 and 16, - - 4.7066 



11. November 17 to December 5, - - 6.1328 



12. December 20 and 21, - - 6.9885 



13. December 29, ... 1.2171 



Annual of Scient. Disc. 1850,^. 221. 



