82 
Supplement to the "Tropical ' Agncultmist." 
[July I 1891. I 
•wicke, it is given as a red resinous exudation 
from Pterocarpus Draco, a leguminous tree. The 
substance would ajjpear to have been valued in 
times past not only for its medicinal properties, but 
also for tingeiug varnishes, especially the varnish 
used in violin manufacture. It is we believe gene- 
rally considered among violin makers that the iden- 
tity of the real Dragon's blood — to which is due not 
only the beauty, but also in some measure the 
richness of tone of old violins, — is now lost, and 
that what is sold at present as Dragon's blood 
is a spurious article which, tliough it closely 
resembles the original, has not its much-desired 
qualities. ThefoUowingis a recipe given by Cooley 
for makingthe facticious Dragon's blood : — Shellac 
4 lb., melt, remove from the fire, and add 
Canada balsam 6 oz. and gum benzoin 2oz.; mix well, 
stir in red sanders wood (or sandalwood) I5 lb ; and 
Venetian red f lb. (both in fine powder) ; and form 
the mass into sticks. In another recipe the 
Venetian red is omitted. 
Resinous exudations from trees of the red or 
ruby colour of Dragon's blood are not unknown in 
Ceylon, but they are objected to either because the 
tint does not quite come up to the standard of that 
of Dragon's blood, orbecause they do not, as is necess- 
ary, mix with turpentine. The genus Pterocarpus 
includes many trees containing red colouring mat- 
ter. From P. Marsupium, the red sandal or san- 
ders wood is derived the red gum kino, which is 
used medicinally by the natives. 
The Ceylon Independent announces the interest- 
ing fact that a committee has been formed, with 
Father Lytton at its head, for taking steps to sink 
an artesian well in a suitable locality. The sum 
of E4000 has been fixed as the amoimt necessary, 
of which the Roman Catholic Mission proposes to 
give RIOOO. The lawyers, who form the bulk 
of the committee, are expected to contribute a 
good round sum. 
The fibre from the musk plant (Abelmoschus 
moschatus) — Like a great many of the malvacese, 
produces a fibre which is said to be as good as any 
for bag and rope making. The seeds, which possess 
a heavy and peculiar odour, are used for flavouiing 
purposes, and at one time sold for over a pound 
sterling per pound weight : but their value has 
gone down, we are told, owing to the discovery of 
a chemical substitute x^ossessing the same proper- 
ties. There are a few of these bushes growing 
and fruiting freely at the School of Agriculture. 
« 
RAIN. 
Rain water, though commonly spoken of as 
jiure, is by no means chemically pure water. It 
always contains a certain amount of oxygen and 
carbonic acid gas which it takes up in its passage 
tlirough the atmosphere. In the vicinity of 
towns it is rendered still more impure by the 
presence of nitric and sulphuric acids, which in- 
crease its disintegrating power on both natural 
and artificial structures. On reaching the ground 
rain takes up more carbonic acid gas, and among 
other things, decaying organic matter: and it is 
to tlie presence of these two substances, together 
with oxygen that its power as a Aveatheriug agent 
is mainly due. While oxygen alters and breaks up 
rocks by oxidising their constituents, and while < 
organic matter brings about the same results by " 
deoxidation, the carbonic acid present in rain water 
forms easily soluble carbonates out of less soluble \ 
compounds. While rain water easily washes 
away the chlorides and nitrates of soda and lime, \ 
most soils are able to firmly retain the phosphoric 1 
acid, ammonia and potash, which are little if at all ' 
found in the drainage water. Even on the heavy 
soils at Rothamsted, and with a rainfall of only 
17 inches, the nitrogen removed every year in ; 
the drainage water from bare follow amounts 
to over 40 lb. per acre, equal to about 2^ cwt. . 
of nitrate of soda. When the roots of a cultivated 1 
crop are present to utilize the nitrates as they : 
are formed in the soil, there is of course much i 
less loss. On the other hand, if rain does cause ; 
a loss of the valuable constituents already pre- j 
sent in the soil, by washing over and soaking j 
through the land, it also imports appreciable ! 
quantities of nitrogen in the form of ammonia j 
and nitric acid from the atmosphere into the 
soil. The rain as it falls in the country in ' 
England has been found to contain about '9 j 
parts per million parts of ammonia, and '19 of nitric ; 
acid. Dew and hoarfrost contain, according 
to Dr. Fream, three or four times the amount of 
ammonia and nitric acid foimd in rain water. 
At Rothamsted the amovmt of nitrogen as 
ammonia in rain, mean of o years, was found 
to be 2 '4 lb. per acre ; nitrogen as nitrates and \ 
nitrites about 1 lb. ; as organic nitrogen a simi- j 
lar quantity : giving a total of 4 '4 lb. per acre. i 
The average of many experiments made on the | 
Continent gives 10"23 lb. of nitrogen per acre 
brought down by the rain. This high average 
is to be explained by the fact that many of the 
determinations were made near towns, where as' j 
a result of thick population and its attendant 
conditions, more ammonia and nitric acid passes \ 
into the atmosphere than is the case in country ] 
places. Warrington gives it that chlorides j 
are always present in rain ; at Cirencester the j 
chlorides in rain water are said to be equal to 40 lb. 
of common salt per acre per annum. At \ 
Rothamsted it was found that 24 lb. of sodium 
chlorides were supplied annually by rain. 
Looking now at the mechanical action of rain, j 
we find that it has a tendency to wash away and i 
carry off the more easily-weathered parts of rocks 
and soils. It is a common exj)erience to find after a 
sharp shower of rain, a number of miniature pillars 
left standing on roads and barelands,^ representing 
either the more durable matter which withstood the 
mechanical action of the rain, or such substance as, 
though not of a durable nature, has been protected i 
from the weather by a pebble or piece of rock ] 
capping it. This simply though forcibly illus- 
trates what goes on around us on a large scale. The ( 
mechanical action of rain water results in the wash- 1 \ 
ing away of soil to a large extent from hill sides, h 
where the transporting power of water is increased ( 
by the gradient of the land. Where the rainfall is I \ 
crowded into limited periods this effect is of course 1 ( 
greater than in places where the same rainfall is 
evenly distributed throughout the year. But what | 
is loss to the cultivator of the hill slopes is generally * 
gain to the tiller of the plains below; transportation 5 
of soil from one place resulting in acciunulation in 1 
another. Another result of the rainfall of a district 1 
