238 [September, 1902.] 
IMPERIAL INSTITUTE JOURNAL. 
Vol. VIII. No. 93. 
occurrence and character they bear a striking resemblance to the coal-bearing series of the 
high veld of the interior. The coal-bearing strata consist of shales, often fossiliferous, sand- 
stones, and coals. They are seamed with dykes and sills of subsequently intruded basaltic 
rocks. Many bores have been put down in the various coalfields, but, in the majority of cases 
where coal was struck, it proved to be of a decidedly authracitic character, although in some 
instances fairly good bituminous coal has been proved to occur. These bores were in all 
cases put down by private syndicates or individuals, with the assistance of Government, for 
the specific purpose of finding coal, and in no case has the bore done more than prove the 
presence of a scam or a basaltic sill, so that nothing is known of the deeper beds of the coal- 
bearing series. The usual succession is as follows. Dwyka conglomerate, black carbon- 
aceous shales, with light coloured sandy-shales (the Ecca shales), sandstones, shales and 
coals (the Ecca coal-bearing series). The chief amount of prospecting and boring has been 
done on the Umlalaas coalfield, the nearest to the Natal railway. I11 a year or two the 
Natal-Zululand railway will be completed as far north as the St. Lucia coalfield, and 
should give an impetus to the development of this and the surrounding coalfields. The 
following is a list of the Zululand coalfields : — 
St. Lucia Bay coalfield (West of St. Lucia Bay). 
Umlalaas coalfield (East of Eshowe). 
Ntambanana coalfield (Lower Umfolosi). 
Umhlatuzi Valley coalfield (North of Eshowe). 
Hlopekulu coalfield (Entonjaneni). 
Qudeni and Madhlozi coalfield (Kkandla District). 
Langagazi coalfield (Nqutu District). 
Nongoma coalfield (Nongonia). 
The Umlalaas coalfield is bounded on the south-east by the sea, and on the north and 
west by the metamorphic rocks of the Engoye mountains ; while to the south-west it merges 
gradually into the series of shales overlying the Dwyka conglomerate which form the 
undulating country towards the Lower Tugela. Unlike the St. Lucia coalfield, the strata 
are not overlaid by basaltic rocks. Most of the seams yet found vary in thickness from a few 
inches to I foot 8 inches, while in one bore 9 feet of alternating shales and coals occurred, 
the aggregate thickness of coal being between 4 and 5 feet. The St. Lucia coalfield 
is situated in the basin of the Nseleni river, and is bounded on the north and south by 
basaltic rocks. Coal-seams, with intercalated shales, occur in thickness from 6 to 15 feet. 
Little or no development has taken place here. Of the other coalfields little is known 
except perhaps the actual presence of a coal-seam. 
Outcrops of the Dwyka conglomerate occur in various districts of Zululand. Its 
presence at the surface in any district is of importance from the fact that in most parts of 
South Africa the ores of metals of economic value occur chiefly in rocks which are older than 
this formation, and therefore have to be looked for below it. On the other hand, all the 
coal-bearing rocks are younger than the Dwyka, and therefore will occur overlying the 
glacial conglomerate. 
Granitic rocks cover an area of over 300 square miles, east of Eshowe, and are of 
common occurrence in the western part of the province. Gold has been found associated 
with these rocks at the former place, where it occurs as very fine wire. 
Basaltic rocks are usually associated with the Sedimentary coal-bearing rocks in the form 
of intrusive dykes or sills, which have forced their way between the beds, and rarely as 
contemporaneous beds which have been erupted during the deposition of the beds. They 
attain their greatest development immediately to the south and east of the St. Lucia coal, 
field. They form the Entondmeni mountains, and the eastern half of the Makowe hills. 
The deposits in the north of Zululand, supposed to contain diamonds because of their fancied 
resemblance to the diamond-producing deposits of Kimberley, have not only been proved 
barren, but the “ yellow ground ” has been shown to be derived from a different rock from 
that of Kimberley, and to occur under different conditions. 
MINING AND CONCENTRATION OF COPPER ORES IN SOUTH 
AUSTRALIA. 
The Wallaroo and Moonta copper mines are situated about 10 miles apart at the 
northern end of Yorke’s peninsula, and are distant about 6 and 1 1 miles respectively, from 
the seaport of Wallaroo, on the eastern shore of Spencer Gulf. There is direct 
communication by rail between the port and the mines as well as to Adelaide. The smelting 
operations arc conducted by the same proprietary at the port of Wallaroo. The mines have 
been in operation for about 40 years. They arc now held under mineral lease from the 
South Australian Government for a lease of 99 years, at a rental of is. per acre per annum, 
and a royalty of 2| per cent, on the declared profits. At the Wallaroo mines there are 
several ore-producing lodes, some of which are nearly parallel, and the general strike of the 
main ore body is about N.75°W. At the Moonta mines there are five ore-producing lodes, 
besides others of less importance: their average bearing is N.30 0 E. The total value of the 
ore produced in connection with these mines has amounted to over ^10,000,000. The 
quantity of vein -stuff raised annually approximates 200,000 tons, giving about 37,000 tons of 
dressed ore. The amount of copper produced at the Wallaroo smelting works is about 
4,800 tons, and the number of hands employed in connection with the mines is about 2,000. 
The main ore-raising operations are conducted at depths varying from 1,000 to 2,000 feet, 
and the deepest workings are now about 2,500 feet from the surface. At the Moonta mines 
the country rock consists of felsite porphyry, a platonic igneous rock of an intensely hard 
character, having a specific gravity of about 2*67. At the Wallaroo mines the rock is 
chiefly a metamorphic mica-schist of possibly Cambrian age. As raised, the ore contains 
2 to 4 per cent, of copper, and needs a comprehensive system of treatment in order to afford 
satisfactory results. The hulk of the ore at the Moonta mines can lie concentrated with 
advantage to a product assaying from 15 to iS per cent, of copper, but at Wallaroo the ore 
contains a larger percentage of iron pyrites and therefore does not usually dress to more than 
10 to 11 per cent., although quite as free from waste as the Moonta concentrates. 
At the Moonta mines the lodes are on the underlay, the dip varying generally from 
50 to 70 degrees. Owing to this and the hard nature of the rock, the shafts are sunk for the 
most part with the lode, wheeled skips being utilized instead of cages for raising the ore to 
the surface. The main hauling shaft, 17 feet by 8 feet, is fitted with a double skip-road. 
At the Wallaroo mines the shafts are usually sunk vertically with cross-cuts extended at every 
120 feet or so. At both mines the practice is to have shutes at the foot of the passes leading 
from the stopes, from which the broken vein-stuff is discharged into wagons in the levels. 
The roads in these levels are set to a slight run, of about A inch to the foot, towards the 
main hauling shafts, so that the loads may be readily handled and the drives kept properly 
drained of water. At the Wallaroo mines the overhead method of sloping is followed, as 
being the most effective and economical in relation to the nature of the rock enclosing the 
lode material, whilst at the Moonta mines both the overhead and underhand systems have 
been followed extensively. The ore, after it is raised to the surface, is dumped on to iron 
screens which shoot the larger rocks in one direction and discharge the smaller in another. 
That which is smaller than 1 { inches is separated into three sizes, the rest is crushed in 
gyratory breakers, and again sorted and concentrated by machinery and hand. For 
concentration after the solid ore has been picked out, the lower grade stuff is passed through 
Cornish rolls and treated in the Hancock jig, which was invented to treat large quantities of 
this class of ore. The Hancock jig consists of a cistern 25 feet long, 4 feet wide and 6^ feet 
deep, made of stout timber, supported by a cast-iron framing over a masonry-loading to give 
it rigidity. In the upper portion of the cistern is suspended a sieve 20 feet by 3 feet, by 
means of four vertical rods which connect it with the machinery giving the pulsating motion 
below. The mesh of the sieve is usually 4 to 5 holes to the linear inch, and on this wire 
bottom there are wooden cross-bars 3 inches apart and' of the same depth, which form 
pockets. These contain a quantity of heavy, coarsely crushed material known as ragging,” 
generally a hard variety of hoematite having a specific gravity of 5, while the ore to be 
concentrated is about 4. The cistern is usually divided into five separate compartments to 
receive the various qualities of ore produced. The cistern is filled with water and the sieve 
entirely submerged. The pulverized vein-stuff after passing through a slime-separator is 
automatically fed on to the head of the sieve, where the ore and waste are separated by the 
pulsating motion imparted, the heavier particles of ore work down through the ragging and 
thence through the wire bottom into the compartments below, while the lighter waste is 
carried on to the tail-end of the jig. The amount of motion in the machine can be easily 
increased or diminished according to the nature of the material which is being operated upon. 
The best concentrates are obtained from the first and second compartments. That from 
the others needs retreating and is often recrushed. 1 5° t° ns °f material may be treated in 
24 hours on one machine ; other machines on the same principle are used for treating coarser 
and finer material. The fine ore which is carried off from the jigs by the flow of water is 
allowed to settle in pits of various sizes, the first being smaller than those succeeding, on the 
principle of the Spitzkasten , and these grade the material to various degrees of fineness. The 
greater part of the slimes is treated on buddies. These revolving tables are either convex or 
concave and are used in sets of four, three being used for a first concentration and one for a 
second concentration of the enriched slime. Following on these is a further treatment by a 
special buddle, and a final concentration on a belt or table vanner. The cost of labour in 
connection with the slime dressing seldom exceeds is. fid. per ton. The coarser tailings 
from the dressing appliances are stacked in heaps and the remaining copper removed by a 
leaching process. The heaps are periodically watered and, by oxidation of the sulphur, the 
copper is obtained in solution, and precipitated in a series of vats and canals by means of 
scrap iron. The precipitate is washed, freed from pieces of iron and despatched to the 
smelting works. This latter method is being greatly extended, so that heaps aggregating 
over 1,000,000 tons may be operated from a central station, on the principle of the method 
used at the Spanish copper mines. 
ORANGE CULTIVATION IN JAFFA. 
The efforts now being made to establish the cultivation of oranges on a large scale in 
several British colonies, and especially in the West Indies, renders it opportune to draw 
attention to an interesting article on the above subject in the current number of the German 
journal Dcr Tropcnpjlauzer (No. 7, 1902, 341), contributed by Messrs. Aaronsohn & Soskin, 
in which a full account of the trade in, and cultivation of, Jaffa oranges is given. It appears 
that, altogether, seven varieties of citrus are cultivated in that district, the following being their 
names and characteristics 
Citrus aurantium (Portuguese orange). This is the Jaffa orange proper, and is the 
one so largely imported into England. It is probably a native of Portugal, but is now 
cultivated in two varieties which have little in common with the original stock. The variety 
popular in England is known locally as Schamuti, and differs from the second and less 
common kind, Belcdi , in being larger and having a thicker skin and no seeds. 
Citrus Bigaradia (Seville orange). — This variety is only grown as a stock for grafting 
purposes, as it has been found that an orange tree raised on this species bears fruit for a longer 
period than when grown in any other way. 
Citrus mcdica (citron). — The two kinds of fruit raised from this species never come to 
England, but are exported to the countries bordering on the Mediterranean, and, to some 
extent also, they find a market among the Jews. 
Citrus limonwn (lemon). — This plant is never grown in Jaffa for the sake of its fruit, 
but, like the hitter orange, is used as a stock on which to graft the sweet orange. It is stated 
that the best and oldest orange trees of Jaffa were entirely raised on lemon stocks, but the 
experience of the present planting community is that trees so raised only bear fruit for 
six or seven years, and are, therefore, less profitable than those propagated from the 
bitter orange. 
Citrus limonum var. dulcis (sweet lemon). — This species is also employed only as a 
grafting stock where orange trees are to be grown on the light sandy soil characteristic of 
some parts of this district. The trees so raised have the advantage of bearing in a short 
time. The sweet lemon itself is popular with the Arabs, and is, to some extent, grown 
at Akka. 
Citrus nobilis (Mandarin orange).- — This tree has been grown in Palestine only for a 
short time, but has spread rapidly. The fruit bears carriage well, and is therefore suitable 
for exportation, whilst the tree is small, and fruits readily. 
Citrus dccumana (grape fruit). — This species is rarely seen, and is nowhere cultivated as 
a crop in the country. 
The production of oranges in the neighbourhood of Jaffa is carried on both by Arabs 
and by Europeans, but the methods adopted by the two classes are identical, with the 
exception that the European planters have, as a rule, adopted machinery where possible. 
One of the chief factors in successful orange culture is efficient irrigation, and every garden 
is provided with a well, from which water can be pumped, either by the primitive Arab 
methods or by the use of oil engines, to all parts by means of stone canals. The ground is 
dug either by direct manual labour, as the Arabs prefer, or by a plough cuffing to a depth of 
from 19 to 3S inches. In this prepared soil seeds of the bitter orange or cuttings of the 
sweet lemon are placed, and the young plants produced from these receive no further 
attention beyond regular watering. After two years’ growth, they are taken up and planted 
out in the orange groves. This transplantation takes place all the year round, without 
distinction of seasons. The young trees are planted very thickly, often not more than four 
or five square yards being allotted to each. After a further two years’ growth in the orange 
garden proper, preparations are made for grafting the true Jaffa orange on the young stocks, 
usually towards the end of the summer season, although there is considerable risk at this 
time of the graft being killed by the cold weather which is apt to come on suddenly. The 
trees begin to yield well four or five years after the ingrafting has taken place ; they 
receive comparatively little attention, hut are watered about once a week, and the ground is 
turned over three or four times a year, in order to facilitate the passage of water to the roots. 
The chief enemies the orange-planter has to contend with are a group of insects resembling 
wood-lice, which infest all parts of the orange trees, and various vegetable parasites, which 
attack both old and young plants, and rapidly destroy them. The Arabs take no precautions 
to prevent the spread of these fungi, and even plant fresh young trees in the neighbourhood of 
old dead trunks covered with vegetable parasites of all kinds, so that an Arab orange garden 
often presents a pitiable spectacle to the eye of a modem cultivator. As regards the future 
of orange cultivation in Jaffa, the authors arc of opinion that the present careless methods of 
the Arabs will, if persisted in, lead to a great killing oft' in production, as has already 
occurred In other orange-growing districts, such as Majorca, Sardinia, and St. Miguel ; 
whilst, if a rational culture under European supervision could be secured, a considerable 
extension of the industry might be made, since, in face of the decreasing output of the other 
orange-growing districts, over-production is scarcely possible. 
