144 Comjwsition of Waters of Land-Drainage and of Rain. 



in November only 0'054 (0"771 parts in a million), or liardly 

 more than a third. The mean quantity for the whole year is 

 008G grains in a gallon, or about 1*228 parts in a million of 

 water.* 



A glance at the column for nitric acid will show how small 

 is the quantity of this substance brought down by rain. Con- 

 siderable variations are observable in this as in the other case, 

 the quantity being in June five times as great as in several other 

 months. The mean quantity is seen to be 0'0315 grains in a 

 gallon, or 0405 parts in a million of rain. 



Before attempting to draw any conclusions from this Table it 

 will be well that we should place the matter in its true bear- 

 ings, by connecting the quantity of ammonia and nitric acid in 

 the rain-water of different months with the quantity of rain 

 which fell in those months. From data furnished me by Mr. 

 Lawes I am able to calculate the number of gallons of rain 

 falling on an acre of land at Rothamsted in each month of the 

 year 1855, and knowing the proportion of nitric acid and am- 

 monia per gallon, nothing of course is easier than to ascertain 

 precisely the total quantity of these substances which was 

 brought in aid of vegetation by this means. 



The Table given below affords these particulars. I hat'e 

 added a column to show the total quantity of nitrogen in the 

 rain, whether existing as ammonia or nitric acid. 



Table VI. — Nitric Acid and Ammonia in Eain-water, per acre, 1855. 



January 



February 



March 



April 



May 



June 



July 



August 



September 



October 



November 



December 



Total in lbs. -whole year 



Gallons 



of 

 Hain. 



13,52.3 

 ^2,473 

 52,484 

 9,281 

 52,575 

 41,295 



157,713 

 59,022 

 34,875 



124,40(5 

 55,950 

 39,075 



Nitric Acid 



in 



Grains. 



Grains. 



230 



944 

 1102 



325 

 1840 

 3303 

 2GS0 

 3577 



732 

 4480 

 1007 



604 



1244 

 2337 

 4513 

 1141 

 4206 

 5574 

 9620 

 4769 

 3313 

 7592 

 3021 

 2438 



2-98 



7-11 



Total 



Nitrogen lu 



Grains. 



1084 

 2109 

 3995 

 1024 

 3939 

 5447 

 8015 

 4870 

 2917 

 7414 

 2749 

 2180 



0-63 



The results in this Table are interesting not only on account 

 of the light which they throw upon the question of drainage, but 



* The experiments of Mr. Lawes and Dr. Gilbert, in 1853 and 1854, gave as a 

 mean, as nearly as possible, 1 part of ammonia in a million of rain. Bous- 

 siiigault's result in Alsace was about 3-4ths that of Lawes and Gilbert. 



