SOILS. 



143 



of rain and snow-water, dew and hoar-frost, 

 collected at Kothamsted from April 1869 to 

 May 1870 inclusive, and the average amount of 



ammonia per million of water found by him is 

 considerably lower than the earlier determina- 

 tions show. The results are given below. 



Table showing the Maximum, Minimum, and Mean Amount of certain Constituents found in Samples of Dew and Hoar- 

 frost, in parts per million. 





Total 



Solid 

 Matter. 



Carbon 



in 

 Organic 

 Matter. 



Nitrogen as — 



Chlorine. 



1 

 Hardness. 



Organic 

 Matter. 



Ammonia. 



Nitric 

 Acid. 



Total 

 Nitrogen. 



Highest proportion, 



Lowest proportion, 



Mean of all, 



80-0 

 26-4 



487 



4-50 

 1-95 



2-64 



1-96 

 0-26 

 076 



2-31 

 1-07 

 1-63 



0-50 

 0-28 

 0-40 



4 55 



1-66 

 279 



8-0 

 3-5 

 5-3 



2f. 



13 

 19 



These small deposits of dew and hoar-frost 

 condensed from the lower stratum of the atmo- 

 sphere contain, on an average, three or four 

 times the amount of organic carbon, organic 

 nitrogen, ammonia, and nitric acid, found in 

 the analyses of rain-water. The total quantity 

 of solid matter, and the amount of chlorides, is 

 also larger, but the difference is much smaller 

 than in the case of the other ingredients. 



Dr. R. Angus Smith, the great chemist, in 



his work entitled Air and Bain, the Beginnings 

 of a Chemical Climatology, 1872, gives the re- 

 sults of numerous analyses of rain-water col- 

 lected both in country and town districts in 

 the United Kingdom. The amounts of am- 

 monia and nitric acid in the rain vary exceed- 

 ingly, according to locality; but the amounts in 

 the rain of country places accord generally with 

 those found in the Eothamsted rainfall pre- 

 viously given. 



Average Composition of Samples of Rain from various districts of England and Scotland, hi parts per million of Water. 





Nitrogen as— 



Chlorine. 



Sulphuric 

 Acid. 





Ammonia. 



Nitric 

 Acid. 



England, country places, inland, 



,, towns, 

 Scotland, country places, sea coast, 



,, ,, ,, inland, 



,, towns, 



,, Glasgow, ... 



0-88 

 4-25 

 0-61 

 0-44 

 3-15 

 7-49 



0-19 

 0-22 



o-ii 



0-08 

 0-30 

 0-63 



3-88 

 8-46 

 12-24 

 3-28 

 570 

 872 



5-52 



34-27 



5-64 



2-06 



16-50 



70-19 



The ammonia of the atmosphere is found to 

 be derived from the decay of animal and vege- 

 table matters, both on land and in the ocean, 

 also from the combustion of fuel, especially 

 coal, hence the richness of rain-water, more 

 particularly in sulphuric acid, which falls in the 

 vicinity of towns. 



Chlorides are principally furnished by . the 

 sea, fine spray of salt-water being carried long 

 distances by high winds. At Cirencester the 

 chlorides in the rain are on the average equal 

 to about 53 lbs. of common salt per acre per 

 annum; at Eothamsted, Hertfordshire, the 

 quantity is about 22 lbs. per acre. 



From the foregoing data it will be seen how 

 entirely inadequate is the amount of combined 

 nitrogen available from atmospheric sources to 

 supply the requirements of different garden 

 crops without some nitrogenous manure. 



It is true that the minor aqueous deposits 

 from the atmosphere, dew, frost, &c, are much 

 richer in plant-food than rain, and there can be 



no doubt that there would be more deposited 

 within the pores of a given area of soil than on 

 an equal area of the non-porous even surface of 

 a rain-gauge. How much, however, of this 

 might be available beyond that determined in 

 the collected aqueous deposits, existing evidence 

 does not afford the means of estimating with 

 certainty. 



Other Sources of Combined Nitrogen. — It has 

 been argued that, in the last stages of the de- 

 composition of organic matter in the soil, hydro- 

 gen is evolved, and that this nascent hydrogen 

 combines with the free nitrogen of the atmo- 

 sphere, and so forms ammonia. Again, it has 

 been suggested that ozone may be evolved in 

 the oxidation of organic matter in the soil, and 

 that, uniting with free nitrogen, nitric acid 

 would be produced. If the supplies of nitrogen 

 from the atmosphere to the soil itself are inade- 

 quate for plant-growth, it may be asked, how 

 about the direct supplies of free nitrogen from 

 the atmosphere to the plant 1 



