Vol. VIII. No. 95. 
IMPERIAL INSTITUTE JOURNAL. 
[November, 1902.] 293 
5. The latex is coagulated by boiling in earthen vessels. This process is said to be 
employed in Mexico. 
These methods need not be referred to in further detail, since they are all more or less 
unsatisfactory, but it may be noted that the fresh latex obtained at Las Cascadas, after being 
slightly diluted with water, was not coagulated even by prolonged boiling, lout if allowed to 
stand until it had assumed a very dark colour it was rapidly and completely coagulated by 
the application of heat. The serum of the latex, which contains a large amount of albuminous 
matter, also showed a similar behaviour. In all the above methods the separation of the rubber 
appears to be brought about indirectly, the added substance really coagulating the albuminous 
matter present, and this coagulum carries with it the rubber globules previously suspended in 
the latex. The rubber thus obtained is, therefore, always contaminated with albuminous 
matter, often containing from 9 to 13 per cent, of the latter, and it is the presence of this 
which makes Castilloa rubber, as usually prepared, so prone to putrid fermentation. The 
value of the rubber would be greatly increased if these albuminous substances could be 
eliminated, either by removing them from the liquid before coagulation, or by bringing the 
latter about in a manner which does not also involve the coagulation of the albumen. 
Methods have been already suggested for accomplishing this in special cases, and a very 
simple process, applicable to Castilloa, is now given by Dr. Weber. It has been observed 
that if Castilloa latex be diluted with water and allowed to stand it “creams,” i.e., the 
rubber globules rise to the surface, but do not unite to form a coherent mass. Dr. Weber 
finds, however, that if formaldehyde be added to the diluted latex the rubber globules, which 
separate, do coalesce to form a cake, while all the albuminous matter remains in the liquid. 
In carrying out the process the crude latex was first diluted with at least five times its volume 
of water, and in dealing with the thick latex obtained at Las Cascadas, it was found advan- 
tageous to dilute with boiling water, but this plan would not be applicable in all cases. The 
diluted latex was then strained through cotton gauze into well-washed petroleum barrels, to 
each full barrel 8 oz. of formaldehyde was added, the whole was well stirred and allowed to 
stand for 24 hours. The formaldehyde prevented any coagulation of the albumen in the hot 
solution, and also caused the rubber to separate as a white mass of such strength and tough- 
ness that it could be lifted entire from the barrel. This mass of rubber is rather porous and 
contains a quantity of the liquid enclosed in its cavities, so that it is at once cut into strips 
which are thoroughly washed with water until quite free from albuminous matter, and then 
dried. The rubber thus obtained is of exceptional purity, it does not undergo any change on 
keeping, and could be used for many industrial purposes without further treatment. The 
dry strips are extremely light in colour, semi-transparent, and, when dissolved in the usual 
rubber solvents, form almost glass-clear solutions ; the characteristic rubber smell is almost 
entirely wanting, the strength is said to be superior to that of washed and dried strips of 
Para rubber, and the behaviour in the vulcanizing process, and the character of the vulcanized 
product are at present under investigation. An analysis of one of the strips showed that it 
contained only 2 '6 per cent, of resinous matter, 0*44 per cent, of ash, and no albuminous or 
insoluble constituents. 
Some interesting observations were also made regarding the amount or resin present in 
the rubber obtained from different parts of the same tree and from trees of different age. It 
was found that in an individual tree the resin increased in amount from the root upwards, 
and that the rubber from the younger trees always contained a far larger proportion of resin 
than that from the older ones. The following table gives the differences observed : — 
Rubber drawn from trunk . 
Percentage of 
resin present. 
. 2 ’6 1 
3 J Si 
3 3 
largest branches . 
377 
5 J 5 J 
33 
medium ,, 
4*88 
s> sj 
33 
young ,, 
S-S6 
?> 5 > 
33 
leaves . 
7 ‘50 
Rubber from 
tree 
2 years old 
* 42*33 
5> 
33 
3 >5 JJ ■ • 
* 35*02 
ss is 
3 3 
4 )> sj 
. 26 ‘47 
53 3 3 
33 
5 )) j> 
. 18*18 
3 3 3 3 
33 
7 >> >> 
• ii *59 
33 3 3 
3 3 
8 . 
. 7*21 
Similar differences have been recorded in a few other cases, and the amount of resin 
present in a sample of rubber would therefore appear to depend not only on the particular 
variety of tree from which it was obtained, but also on the age and to a less degree on the 
part from which the latex was drawn. The above figures indicate that in the case of 
Castilloa it would not be advisable to tap the trees until they are at least 8 years old, 
not only in the interest of the life and development of the tree, but also in the amount of 
resin which may be safely admitted in rubber of high quality. 
In conclusion, Dr. Weber gives some particulars concerning the prospects of rubber- 
planting in Central America, and one point mentioned is of interest to all intending planters 
of Castilloa elastica. It is stated that there are three varieties of the tree, viz., alba, negra 
and rubra, distinguishable only by the colour of the bark, but of very different value as rubber 
producers. The alba has a white bark of a distinct yellowish or pinkish cast ; it is the 
hardiest of the three varieties, suffering little from the tapping process ; it . produces a thick, 
creamy latex, and yields the largest quantity of rubber. The negra has a very rough, dark 
bark ; it readily yields a thin milk, producing a good rubber, but the tree may be easily bled 
to death in tapping. The third variety, the rubra , has a reddish bark which is very smooth, 
thin and brittle, and does not show the longitudinal furrows noticeable in the other two ; it 
yields a very small quantity of latex, but the quality of the rubber is good. The rubra is 
very common all over Central America, and it is possible that it has been planted in a number 
of instances instead of the alba ; indeed, Koschny is inclined to think that it was the rubra 
variety which gave such discouraging results in Ceylon and Java. In planting Castilloa, 
therefore, great care would appear to be necessary in order to make quite sure that the seeds 
or seedlings employed are really those of the best variety. 
THE ECONOMIC PLANTS OF THE SUDAN. 
In an article contributed to the current number of Der Tropmpjlanzer Dr. J. J. David, 
who has recently made a journey through Egypt and the Sudan with the object of ascertaining 
what openings for German trade exist in those countries, gives some information regarding 
the natural products of the Sudan, from which the following particulars have been compiled. 
Tamarinds . — The East Indian tree Tamarindus Indira grows naturally to a small extent 
in Kordofan, but is especially abundant along the Blue Nile, where it bears fruit from June to 
August. The Kordofan supplies of pulp extracted from the fruit are all consumed locally, 
but from the Blue Nile districts considerable quantities are sent into Lower Egypt. The tree, 
in addition to producing pulp, is useful as a shade-tree and a wind-breaker, and for the latter 
purposes the author thinks it is better suited than the Parkinsonia species which the Govern- 
ment is now planting in the neighbourhood of Omdurman. No attempt is at present made 
to cultivate the tamarind, and the pulp is sent into the market mixed with seeds and fibre, 
and it is suggested that an improvement in the quality of the product and an extension in 
trade could be secured by attention to these points. 
Gum Arabic .■ — Before the days of the Dervish revolt Sudanese gum, derived from 
various species of acacia, was in great demand in Europe, where, owing to its ready solubility, 
adhesive properties and absence of colour, it brought better prices than the gums from 
Senegambia, Persia, India, etc. Since the suppression of the rebellion the gum trade has 
only slowly begun to recover itself, owing to the great depopulation of the country which 
occurred during the Dervish rule. The trade is at present almost entirely in the hands of 
Greek and Jewish merchants, who buy this commodity in small quantities along the White 
Nile from Arabs who have transported it down stream. The gum is collected by native 
shepherds, who make incisions in the trees during the winter months ; from the cuts then 
made gum begins to flow in March and, with the advent of the dry season, hardens into 
4 tears/ which are then collected. That the trade is slowly being re-established is evident 
from the fact that the price of gum has risen from five shillings in 1900, to twenty -five shillings 
per cwt. in Kordofan at the present time. The latest statistics of export available are for 1900, 
when 44,000 cwt. were sent north by the military railway. 
Cotton. — A variety of Gossypium herbaceum, different from that furnishing the valuable 
long staple Egyptian cotton, is grown throughout the Sudan, including Darfur and Equatoria, 
and yields a cotton of c fineness ’ and * length 5 suitable for working. Egyptian cotton has, 
however, also been experimentally introduced into Tokar, Taka and Gallabat in the western 
part of the country. The natives sow their cotton during the rains in sufficient quantity 
only for their household needs. Cultivation on a more extensive scale has, however, now 
been undertaken by several Egyptians cotton dealers, who have purchased large tracts of land 
for this purpose in Berber and intend to inaugurate improved systems of cultivation to 
produce a fibre suitable for export in large quantities. 
Sugar. — The sugar cane, although widely cultivated in Egypt, is not much grown in the 
Sudan, its place being taken by Sorghum saccharatum , which appears to be indigenous to the 
country and is known to the native as 4 ankohb.’ This plant requires less water for its 
successful cultivation than cane ; it is planted usually in August and reaped in the following 
January. Like cotton only sufficient for local needs is grown. Although before the revolt 
small factories for sugar manufacture existed in Gedaref and Gallabat, all the sugar required 
is now imported from Europe, {cf. Imp. Inst. Journ. 1900, 210.) 
Senna. — This drug is cultivated principally in the southern plains of the Sudan and is 
brought into the Berber, Khartum and Omdurman markets by the Bedouins. It is used locally 
and in Egypt in the form of an infusion for dysentery and is an ingredient in a refreshing 
drink in vogue among the Sudanese. The leaf collected is that of Cassia obovata ; the price 
in 1 900-1 90 1 varied from 7s. 6d. to 10s. for bales of 200 lb. 
Indigo. — This dye was formerly prepared from Tephrosia apollinea , and probably also 
from Polygala tinctoria , in the eighth and ninth centuries, and records are still in existence oi a 
factory at Kamlin on the Blue Nile, but the industry has now entirely disappeared, although 
the soil and climate in this neighbourhood are eminently suitable for the cultivation of indigo- 
yielding plants. 
Rubber. — Cakes and balls of rubber are from time to time offered in the Sudanese 
markets, but their origin is unknown. From their sticky character, however, they appear to 
be produced from a species of Landolphia. 
In this connection it should be mentioned that on the occasion of Colonel Spark’s 
expedition to the Bahr-el-Ghazal in 1899 several samples of rubber and gutta-percha were 
collected from unidentified trees in that neighbourhood, and were subsequently examined in 
the Scientific Department of the Imperial Institute. The rubbers contained a large pro- 
portion of pure caoutchouc and a small amount of resin, and were valued by brokers at from 
is. iod. to 2s. 3d. per lb. The gutta-perchas collected at the same time were, however, not 
of a valuable character. The promising nature of these rubbers has led the Administrator of 
the Sudan to appoint an expert who is at the present time investigating the rubber-yielding 
trees of the country. 
Cereals. — The principal food plant grown is Sorghum vulgare , locally known as 
4 DJrnrr a.’ This is sown in the season May to July, during the rising of the Nile, and is 
generally ready for cutting in about 60 days. The ease with which it can be cultivated led to 
a large production in former days, when the excess was exported to Egypt — a state of things 
which will doubtless occur again in the near future when the country recovers from the 
ravages of the late rebellion. 
In the Western Sudan 4 Dhurra’ is replaced by the 1 Millets/ Panicitm miliaceum and 
Penicillaria species, or by 4 Telabun ’ {Eleusine coracana), since in this district irrigation of the 
land is not such a difficult problem as in the other parts of the country. In the basin of the 
Blue Nile near P'ashoda both sorghum and true maize are grown on the black alluvial soil 
deposited by the river. It is computed that about two-thirds of the corn produced by the 
cereal plants here enumerated is used for the production of native beer. The author 
concludes by drawing attention to the slow but certain improvement of trade and commerce 
under the new regime , and regards the present time as auspicious for the establishment of 
planting and similar enterprises under European supervision. 
MINERAL RESOURCES OF VANCOUVER ISLAND. 
The mineral resources of Vancouver Island comprise coal, gold ores, copper-gold ores, 
with a little galena and magnetite. Although the first discovery of coal was made on the east 
coast of the island as early as 1835, no systematic prospecting or developing was commenced 
until 1849, when the Hudson’s Bay Company brought a party of coal miners from Scotland 
and commenced work at Suquash, About 1852 the Company abandoned work at this point, 
and commenced mining for coal on the present site of the city of Nanaimo. In 1862 
Mr. Dunsmuir discovered the Wellington Seam, on the Nanaimo River, and later formed a 
company which built the Esquimalt and Nanaimo Railway, and opened the Northfield, 
Union and Extension Collieries. 
The history of metalliferous mining commenced with the discovery of placer gold on 
the Leech and Sooke Rivers, about twenty miles from Victoria, in i860. These discoveries 
were succeeded later by others on the China and Granite Creeks, but it w*as really not until 
the commencement of the Klondike excitement that any really serious efforts were made in 
prospecting even the coast line on the western side of the island. Since then gold-bearing 
quartz, partially free-milling, copper ores, and iron ores have been discovered on Lhe west 
coast, occurring in zones having a general trend to the north-west, as well as copper-gold ores 
in the south-eastern portion of the island on Mounts Mallahat, Skerrit, Sicker and Brenton. 
The Geological formation of the island may roughly be divided into three separate classes oi 
rocks, viz : — (1) Cretaceous sandstones and shales, in which occur the coal measures ; (2) a 
belt of semi-crystalline slates ; (3) Dawson’s Vancouver Series which, according to his classifi- 
cation, embrace the igneous and metamorphic rocks, together with crystalline limestones. A 
very large portion of Vancouver island has not been explored and the geology of the country 
is only very imperfectly known, but it appears to be complicated, for whilst the zones of country 
rock have some regularity as regards strike and dip, yet the innumerable and extensive faults 
have greatly added to the difficulties in prosecuting and development work. There are no 
leads, and the ore bodies occur principally as lenses, either at the contact of igneous dykes 
and limestone, or in fissures in igneous rocks, or as lenses in schistose rocks. These lenses 
often occur in zones, and from their various outcroppings give the appearance to an inexperi- 
enced miner of a true fissure lode. Hornblende, containing an unusually large percentage 
of iron, forms extensive deposits. 
