198 MANURING COFFEE. 
- analysis, so, in the absence of observed facts, it may 
' be excusable to speculate a little on the subject. 
There can be little doubt that the atmosphere is the 
primary source of the nitrogen in plants. The atmo- 
sphere is anterior to the soil in our cosmogony, is in fact 
the great agent by which the soils have been produced, 
and nitrogen not being a constituent of the primary 
rocks must have been absorbed from the atmosphere in 
the first instance ; ergo, all the nitrogen in plants comes 
directly or indirectly from the atmosphere; so in this 
- sense Ville’s expectation is present reality. When one 
considers how important atmospheric combined nitrogen 
is to plants, this element constituting, according to 
- Johnstone and Cameron, 13 per cent of their weight, 
it is matter for wonder that it should be present in such 
emall proportion in the air, and one would be a priore 
disposed to credit the conclusion which Ville early 
arrived at from his experiments of 1849-1855 that plants 
can assimilate free nitrogen ; but English chemists are 
diametrically opposed to this view. It is so extremely 
difficult to estimate accurately the combined nitrogen 
in the air, that experimenters mostly confine themselves 
to the estimation of that in rain water. Perhaps the 
most reliable published results are those of Dr. Angus 
Smith, who gives the following :— 
Rain WATER IN PARTS PER MILLION. 
Where Ammo- Albuminoid Nitric 
collected. nia. ammonia, acid. 
Ireland, Valencia... eS ‘0: 37 
Scotland, five sea-coast 
country places, West... °48 “ py 
Scotland, eight sea. coast ait 
country places, Hast... °99 ‘Il “AT 
Seotland, twelve inland 
country places joo, 5B) "04 “31 
England, twelve inland 
country places spall OY “ty 75 
Calculating the averages we would get ammonia ‘78, 
albuminoid ammonia ‘08, and nitric acid 49, or a 
total of °835 of combined nitrogen in one million parts 
of rain water. Now the weight of a cubic inch of 
water is ‘0361 lb., and an acre contains 6,272,640 
square inches. A rainfall of one inch therefore weighs 
226,442 lb. per acre of which ‘189 lb. is nitrogen. A 
rainfall of 80 inches per annum would only supply 
567 lb. of nitrogen per acre, a rainfall of 100 inches, 
like that of Ceylon, 18°9 lb. Suppose we take a crop 
of potatoes at not less than 4 tons per acre, of which. 
2:1 per cent is nitrogen; no less than 188 Ib. of 
nitrogen per acre would be carried away in a single 
crop of which the rainfall of the whole year could 
only supply 5°67 Ib. 
