82 
Supplement to the "Tropical ' /igrtcultimst.” 
[July I 1891. 
wicke, it is given as a red resinous exudation 
from Pterocarpus Draco, a leguminous tree. The 
substance wo>ild appear to liave been valued in 
times past not only for its medicinal properties, but 
also for tingeing 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, though it closely 
resembles the original, has not its much-desired 
qualities. The following is a recipe given by Cooley 
for making the facticious Dragon’s blood : — Shellac 
4 lb., melt, remove from the lire, and add 
Canada balsamfios. andgum benzoin 2oz.; mi.x well, 
stir in red senders wood (or sandalwood) lb ; and 
Venetian red J lb. (both in line 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, or because they do not, as is necess- 
ary, mi.x with turpentine. The genus iVerocarpita 
includes matiy trees containing red colouring mat- 
ter. From P. Marmphm, the red sandal or san- 
dors wood is derived the red gum Idno, wdiich is 
used medicinally by the natives. 
The Ceyhn Independent announces the interest- 
ing fact that a committee has been formed, wdtli 
Father Lytton at its head, for taking steps to sink 
an artesian weU in a suitable locality. The sum 
of E4CVX) has been fixed as the amount necessary, 
of which the Roman Catiwlic Mission proposes to 
give BIOOO. The lawyers, tvho form the bulk 
of the committee, are expected to contribute a 
good round sum. 
The fibre from the musk plant (Abehnoechua 
mosehatua ) — Like a great many of the malvucore, 
produces a fibre which is saici to be ns good as any 
for bag and rope making. The seeds, which possess 
a heavy and peculiar odour, are used for llavouring 
puri)oseB, and at one time sold for over a pound 
sterling per pound weight : but tlniir value has 
gone down, we are told, owing to the discovery of 
a chemical substitute iiossessing 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 ns 
pure, 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 
through 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 stmctures. On reaching the ground 
rain takes up more carbonic acid gas, and among 
other things, decaying organic mattor: and it is 
to the presence of these two substances, together 
with oxygen that its power as a weathering 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 rein water 
forma 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 
acid, ammonia and potash, which are little if at all 
fonnd 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 w'ater from bare follow amounts 
to over 40 lb. per acre, equal to about cwt. 
of nitrate of soda. When the rootsof a cultivated 
crop are present to utilize the nitrates as they 
are formed in the soil, there is of course much 
less loss. On the other hand, if rain does cause 
a loss of the valuable constituents already pre- 
sent in the soil, by w'ashing over and soaking 
through the land, it also imports appreciable 
quantities of nitrogen in the form of ammonia 
and nitric acid from the atmosphere into the 
soil. The rain as it falls in the country in 
England has been fonnd to contain about ’9 
parts permillion 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 add found in rain water. 
At Rothamsted the amount of nitrogen as 
ammonia in rain, mean of 13 years, was found 
to bo 2'4 lb. per acre ; nitrogen a.s nitrates and 
nitrites about 1 lb. ; as organic nitrogen a simi- 
lar quantity : giving a total of 4'4 lb. per acre. 
The average of many experiments made on the 
Continent gives I0'2H lb. of nitrogen per acre 
bronght down by the ruin. This high average 
is to be e.xplained by the fact that many of the 
detonninationa were made near towns, where ns 
a result of thick population and its attendant 
conditions, more ammonia and nitric acid pastes 
into the atmosphere than is the case in country 
places. Warrington gives It that chlorides 
are nlwaj^ present in rain ; at Cirencester the 
chloridesihrainwaterareaaid to boeqiial to 401b. 
of common salt per acre per annum. At 
Rothamsted it was found that 24 lb. of sodium 
chlorides were supplied annually by rain. 
liooking now at the mechanical action of rain, 
we find that It has a tendency to wash away and 
carry off the more easily-weathered parte of rocks 
and soils, ft is a common experience to find afteia 
sharp shower of rain, amunber ofmiuiaturo pillars 
loft standing on roads and bare lauds, representing 
either theraore durable matter wliich withstood the 
mechanical action of the rain, or such substance as, 
thn\igh not of a durable nature, has been protected 
from the weather by a pebble or piece of rock 
capping it. This simply though forcibly illus- 
trates what goes on aroimd us on a largo scale. The 
mechanical action of rain water results in the wash- 
ing away of soil to a large extent from hill side»i 
whore the transporting power of water is iuoreased 
by the groilieut of the land. Where the rainfall i> 
crowded into limited periods this effect is of course 
greater than in places where tlie same rainfall ie 
evenly distributedthroughout the year. But what 
is loss to the cultivator of the hill slopes is generally 
gain to the tiller of the plains below; transportation 
of soil from one place resulting in accumulation in 
another. Another result of the rainfall of a distrlflt 
