ATMOSPIIKlilC Ain AS THE FOOD OF PLANTS. 87 



to detect. The greatest proportion of nitric acid found in 

 rain occurred in a slow-fiilling morning shower, (9th Octo- 

 ber, 1857, at Liehfrauenberg), viz., 62 parts* in 10 million 

 of water. In fog, on one occasion, (at Paris, 19th Dec, 

 1857,) 101 parts to 10 million of water were observed. 



Knop found in rain-water, collected near Leipzig, in 

 Jidy, 1862, 5G parts; in rain that fell during a thunder- 

 storm, 98 parts in 10 million of water. 



Boussingault found in rain an average of 2 parts, in 

 snow of 4 parts, of nitric acid to 10 million of water. 



Mr. Way, whose determinations of ammonia in the at- 

 mospheric waters collected by Lawes and Gilbert, at 

 Rothamstead, during the whole of the years 1855-6, have 

 already been noticed, (p. 63,) likewise estimated the nitric 

 acid in the same waters. He found the proportion of ni- 

 tric acid to be, in 1855, 4 parts, in 1856 4^ parts, to 10 

 million of water. 



Bretsehneider found at Ida-Marienhiitte, Prussia, for the 

 year 1865-6 an average of 8^ parts, for 1866-7 an average 

 of 4^ parts, of nitric acid in 10 million of water. At Regen- 

 walde, Prussia, the average in 1865-6 was 25 parts, in 

 1866-7, 22 parts. At Proskau, the average in 1864-5 was 

 31 parts. At Kuschen, the average for 1864-5 was 6 

 parts; in 1865-6,7; in 1866-7, 8 parts. At Dahme, in 

 1865-6, the average was 12 parts. At Insterburg, Pincus 

 and RoUig obtained in 1864-5, an average of 12 parts; in 

 1865-6, an average of 16 jtarts of nitric acid in 10 million 

 of water. The highest monthly average Avas 280 parts, 

 at Lauersf )rt, July, 1S64 ; and the lowest was nothing, 

 April, 1865, at Ida-Marienhiitte. 



Quantity of IVitric Acid in Atmospheric Water, — The 

 total quantity of nitric acid that could be collected in the 

 rains, etc., at Rothamstead, amounted in 1855 to 2.98 lbs., 

 and in 1856 to 2.80 lbs. per acre. 



* In all the quaiititative statements here and elsewhere, anhydrous nitric add, 

 Ny Oj, (O— 10, formerly NOj, 0—8) is to be understood. 



