Composition of Waters of Land-Drainage and of Rain. 143 



Paper a still greater importance, inasmuch as the facts now ascer- 

 tained have a large and comprehensive meaning, and are inti- 

 mately associated with both the philosophy and practice of 

 agriculture. 



The methods which I have employed for the determination of 

 nitric acid and ammonia in rain-water will be found fully 

 described in an Appendix to this paper. We shall here there- 

 fore occupy ourselves only with the results. 



The rain gauge used by Mr. Lawes at Rothamsted is of a very 

 large size, being of an area exactly roVoth of an acre. The 

 water falling in this gauge is accurately weighed morning and 

 evening. In the ' Gardener's Chronicle,' and elsewhere perhaps, 

 Mr. Lawes has published from time to time the results of his 

 observations, and it may be remarked in passing, that by com- 

 parison with an ordinary small gauge, the large collecting arrange- 

 ment is found to indicate a rain-fall larger by several inches in 

 the year. The gauge, which is of wood, lined with lead, is 

 placed in the centre of a field far from any source of contamina- 

 tion, at more than 20 miles from London, and about 4 miles from 

 the nearest market town, which is St. Albans. 



The series of waters supplied to me by INIr. Lawes repre- 

 sented the whole rain -fall of each month in the year 1855. That 

 is to say, the water falling on separate days during each month 

 has been mixed together, and upon a portion of this mixture the 

 analysis has been made. 



The following Table shows the amount in grains of nitric acid 

 and ammonia in an imperial gallon of the rain of different 

 months : — 



Taf.le Y. — Xitric Acid and Ammonia in Rain-water, 1855. 

 (Grains in the imperial gallon.) 



.January 

 February 

 March .. 

 April .. 

 May .. 

 June 

 July .. 

 August 

 September 

 October 

 November 

 December 



It will Ik- seen Iroin tliis Table that the quantity of ainnionia 

 in the rain of diflercnt months varies considerablv, l)eini; in June 

 as much as 0'135 grains in a gallon (I'Oo parts in a million), and 



