MANURING COFFEE. 199 
Coffee contains rather more nitrogen that the potash, 
_viz., 2°14 per cent., not reckoning, for want of data, 
the parchment skin. A 5 ecwt. crop thus carries away 
only 12lb. of nitrogen, while our rainfall of 100 inches 
as per Smith’s analysis contains nearly 7 lb. in excess 
of the demand for the crop. Mr. Horsfall assumes 
that 200 leaves are dropped per tree per annum ; Mr. 
Fraser of Damboolagalla assumes 2,000: we may assume 
that while 2,000 are dropt 200 are irrecoverabiy lost by 
wind and wash. This according to Mr. Hughee would 
remove other 6°6 lb. of nitrogen per acre, still leaving 
a balance of 41b. to the credit of rainfall. Jf we 
knew what allowance to make for the parchment we 
should not have this balance; but in any case the 
result would be very different from a heavy crop 
like the potato which carries away 182°3lb. in excess 
of the calculated rain supply. It is found however, 
that the greater the rainfall the smaller is the per- 
centage of nitrogen, vide table—east of Scotland has a 
smaller rainfall, but higher proportion of nitrogen, than 
the west of Scotland, and dew has a much _ higher 
proportion than ordinary rain. 
But there is still another most important factor to 
be taken into account. Boussingault found that when 
the atmosphere was in a high electrical condition the 
proportion of nitric acid in the rain was enormously 
increased. In ordinary circumstances he found only 
about ‘02 per 100,000 parts ; in a hail storm, however, 
the atmosphere being highly electrical, the rain con- 
tained not less than 55 and the melted hail 8:3 parts 
of that acid (Hassal). Let us suppose the rain and 
hail’ together contained no more than 7; an inch of 
such rainfall (and thunderstorms of an inch of rainfall 
are not uncommon in Ceylon) would contain 15°85 1b, 
of nitric acid, or rather more than 4 1b. of nitrogen, 
and an inch and a half of such rain would contain 
more nitrogen than the whole annual rainfall of 30 
inches calculated from Dr. Angus Smith’s analyses. 
I have been informed by a Colombo gentleman who 
has collected rain during thunderstorms in Colombo, 
that he has been surprised at the strong smell that 
was shortly developed in it. This odour could be of 
no other than nitrogenous origin. I think, therefore, 
there is every reason to believe that the atmospheric 
supply of nitrogen to the plants, in the tropics, is 
greater than in temperate countries, and when the 
soil is prepared to receive this nitrogen, it so far 
replaces the necessity for nitrogenous manure. 
I meant to have said a word about the fertilizing 
power of gyysum in the soil beirg less, if atall, due 
to its power of fixing atmospheric ammonia than to 
