320 [December, 1902.] 
IMPERIAL INSTITUTE JOURNAL. 
Vol. VIII. No. 96. 
the report to the advisability of cultivating the lime tree, Citrus medica , which is already 
widely distributed, and from which lime-juce, calcium citrate, and the volatile oil of limes 
could be profitably manufactured. Five varieties of pine-apple are indigenous, two of which 
at least are suitable for table use ; the Maingard, under cultivation, occasionally produces here 
fruits weighing from 15 to 20 lb., which could be placed on the European market from 
November to January, during which season the supplies from other countries are not 
available. 
The sugar-cane is also cultivated, and from the juice a kind of cider is prepared, but the 
production of spirit has now almost ceased, owing to the competition of Mauritius rum, 
■which Is imported to the extent of over 15,000 gallons annually. 
An essential oil industry might also be created in the colony, since the various citrus 
species, ylang-ylang, vetivert, patchouli, pelargonium, and sandal wood, all yielding 
essential oils used in medicine and perfumery, are indigenous to the islands. 
THE WITWATERSRAND MAIN REEF SERIES. 
In a paper read before the Institution of Mining and Metallurgy, Messrs. T. A. Leggett 
and F. H, Hatch discussed the gold production and life of the Main Reef series down to a 
depth of 6,000 feet. One of the earliest estimates was that made by Messrs. Hatch and 
Chalmers in 1S95, who forecasted a production from Witwatersrand generally within half 
a century of £700,000,000 sterling. For this estimate an average milling width of 3 feet 
was assumed for the whole Rand ■ the yield was averaged at 38s. per ton, and it was 
assumed that the reef would be worked down to a vertical depth of 3,500 feet. 
More recently Mr. J. Hays Flammond estimated a total production from the central 
section of the Rand of £600,000,000, and from the east and west sections £200,000,000, 
and puts the future duration of profitable operations on a large scale at less than twenty- 
five years. In contrast to this Mr. W. Bleloch estimates the gold available for practical 
mining in the area between Randfontein on the west, and Halfontein on the east, at 
2,871 millions sterling. In this estimate the vertical depth to which mining will be carried 
is put at 7,000 feet for the richer central section of the Rand ; at 3,000 feet for the 
Vogelstrius to Paarl Central Section, and at 6,000 feet for the remainder. The present 
writers have collated the facts on which such estimates can be based, and have thence 
deduced as fair a one as is possible under the circumstances. The geological character of 
the Witwatersrand conglomerates is now pretty well understood. The sheets of “banket” 
outcropping along the Rand have been proved to be gold-bearing for a distance along 
the strike of 47 miles. The continuity in depth has been proved by boreholes, e.g., 
in the : — 
Violet borehole (dip of the Randfontein Series) to a depth of 
New Rand Mines (dip of the Aurora West) to a depth of 
Geduld (dip of the Modderfontein Series) to a depth of 
Rand Victoria (dip of the Simmer and Jack) to a depth of . 
Beguidenville (dip of the City and Suburban) to a depth of . 
Angelo Deep (dip of the Angelo) to a depth of . 
TurfFontein (dip of the Village Main Reef) to a depth of 
1,884 feet. 
2,040 ,, 
2,136 „ 
2,39i ,, 
3 A 30 ,, 
3,783 „ 
4,887 „ 
The one point on which there is little evidence is the gold contents of the conglomerate 
beds at depths of 4,000 feet to 5,000 feet. The borehole assays have proved that they do 
carry gold in variable quantity, but it is not possible to make any deductions from 
half-a-dozen samples from boreholes miles apart, especially as the gold occurs in pockets 
or similar segregations of the precious metal. The even grade is only maintained by 
keeping the development well ahead of the mill and drawing the ore from a number of 
stopes of different value. Therefore the average value for any section of the reef can only 
be determined by practical trials over long periods. The following estimate is based on 
the assumption that the Main Reef Series will be worked to a vertical depth of 6,000 feet. 
Mining properties are to-day being sold where the reef lies at a depth of 8, 000 feet and 
over, and companies are in course of formation with the object of developing these 
areas. It is, however, impossible at present to fix a limit to the depth to which mining 
operations may ultimately be carried, because of the many indeterminate factors entering 
into the problem. The depth at which it has been proved possible, under ordinary 
conditions, is 6,000 feet, and forms the basis of most mining calculations. In estimating the 
value of the reefs of the Rand the area was divided into sections, and the following factors 
determined in each case : — 
(<z) Average length in feet of reef along the strike. 
[b) Average “backs” (or length along the dip) in feet, down to a vertical depth of 
6,000 feet. 
(<r) Average milling width in feet. 
(d) Average percentage deduction for unpayable ground, dykes, safety pillars, etc. 
(e) Average yield, per ton, in pounds sterling. 
The estimated total production of gold in pounds sterling for any section, then, is — ■ 
( a x b x c , ) 
{ d \ x e 
t 12 ) 
where one ton is represented by 12 cubic feet. Factor a was obtained by direct measure- 
ment ; b by measurement on geological transverse seetions. The milling width c was the 
width of reef actually sent to the mill, obtained by deducting from the known sloping 
width a percentage equivalent to that of the waste rock sorted out. Factor d is an 
arbitrary amount varying with the character of each section. In the richer mines a deduc- 
tion of 5 to 10 per cent, was made, while in the lower grade mines as much as 30 to 50 
per cent, of the total reef tonnage was rejected. Factor e is the average yield of the mines 
comprised in each section for the five years ending October, 1S99. The sections are the 
following : — 
No. 1. 
1 J 
2. 
3- 
3 ? 
4 
3 3 
5 
33 
6. 
3 3 
7 
3 3 
00 
33 
9 
>3 
10, 
3 3 
11. 
33 
12 
33 
x 3' 
Radfontein “A” Block inclusive, to Luipaardsvlei (West Boundary). 
Luipaardsvlei (West Boundary) to Grey’s Mijnpacht, inclusive. 
West Roodepoort to Durban Roodepoort, inclusive. 
Kimberley Roodepoort to Bantjes, inclusive. 
Aurora West to Paarl Central, inclusive. 
Langlaagte Royal to Crown Reef, inclusive. 
Johannesburg Pioneer to City and Suburban, inclusive. 
Meyer and Charlton to George Goch, inclusive. 
Plenry Nourse to Jumpers, inclusive. 
Treasury to Glencairn, inclusive. 
Knights to Balmoral, inclusive. 
Ginsberg to Blue Sky, inclusive. 
Chimes West to Modderfontein Extension, inclusive, 
The average yields from 1894 to 1899, from which factor e was obtained, are shown 
in the first half of the following table, and alongside is given the estimated production 
Average Yields 1894-1899. 
Estimated Total Production. 
Section. 
Total tons 
milled. 
Total 
value. 
Value 
per ton 
milled. 
No. of 
mines. 
Length 
along 
reef in 
miles. 
Estimated total 
production. 
Amount 
already 
produced to 
Dec. 31, 1901, 
Estimated 
future 
production. 
No. 
1 
2 
3 
4 
5 
6 
7 
8 
9 
10 
11 
12 
13 
727,107 
973 , T 4 ° 
1,422,840 
178,440 
L 46 S. 35 S 
3,030,500 
4,405,416 
1,752,838 
r, 994 , 7 i 2 
6,808,877 
624,581 
1,059,888 
1,378,164 
£ 
1 , 343,310 
1 , 733,655 
3.049.769 
221,370 
2,103,989 
5,770,070 
12,237,864 
2,827,816 
4 , 58 l,IH 
12,159,848 
862,451 
2,334,042 
2 . 095.770 
S. 
36*95 
35*62 
42*87 
24’8l 
28*72 
38*13 
65*56 
32*27 
45*93 
35*72 
27*62 
44*04 
30*41 
4 
9 
6 
2 
8 
5 
12 
4 
5 
11 
2 
4 
5 
5*464 
4*924 
2*273 
3*324 
5*398 
1*553 
2*600 
1*756 
2*197 
3 ' 75 o 
1*572 
4*015 
8*049 
z 
124.376.000 
115.847.000 
33.059.000 
18.197.000 
97.606.000 
99.765.000 
231.546.000 
52.713.000 
94.705.000 
213.423.000 
24.180.000 
107.112.000 
97.794.000 
£ 
1,627,637 
2,192,840 
4 , 347,032 
285,170 
3,410,320 
9 , 125,945 
20,416,707 
4 , 061,352 
5 , 934,616 
16,606,250 
999,794 
2,462,667 
2,767,645 
£ 
122,748,363 
II 3 > 654 ,l 6 o 
28,711,068 
17,911, '29O 
94 , 195,680 
90,369,055 
211,129,293 
48,651,648 
88,770,384 
196,816,750 
23,180,206 
104,649,333 
95 , 026,355 
Totals 
25,821,861 
5 1 , 3 2 8, 065 
3976 
77 
46*875 
1,236,084,485 
Ban 
ks, C 
ustoms 
works, etc. 
2 , 523,776 
2 , 523,776 
1,310,323,000 
76,762,291 
1 , 233 , 560,709 
For the three years preceding the war the average increase of production was at the 
rate of ,£4,000,000 per annum, the production for 1899 being about £"19,000,000. Allowing 
18 months from January, 1902, for the industry to be restored to the conditions existing in 
August, 1899, a similar increase of production would bring the output to at least £30,000,000 
by June 30, 1906, and if this rate of production were maintained from that time onwards, 
the total production of £1,233,560,709 would give a life from January, 1902, of 42! years. 
As, however, the production will decline gradually, the life of the industry is likely to be 
prolonged a considerable number of years beyond the time indicated. 
THE IRON RANGES OF NORTH-WESTERN ONTARIO. 
Although the iron ranges of the upper part of the Lower Huronian are far more 
extensively developed in Ontario than other varieties of iron-bearing rocks, yet examples of 
other kinds of iron ore deposits are found in the province. Those of the Lower Pluronian, 
which are the oldest as well as the most important, may be divided into three well-marked 
types : that of the iron range proper, which is apparently the uppermost group ; lenses of 
magnetite interbedded with green schist, as at the Atikokan river ; and titaniferous magnetites 
associated with basic eruptives. Parallel with these ancient western iron ore deposits should 
perhaps be placed the magnetites of Eastern Ontario, which are associated with what are 
usually called Upper Laurentian rocks, probably the equivalents of the western and northern 
Pluronian. Ascending to the Animikie, which is perhaps Lower Cambrian, we find the largest 
and most easily worked iron mines in the world in the Mesabi range in Minnesota, but no 
workable deposits have yet been discovered of this age in Ontario. Belonging to the 
Pleistocene age are the bog ores of Charlotteville town and the magnetic iron sands widely 
found near Peninsula, north of Lake Superior. 
The most widely spread of the iron-bearing rocks of Ontario, as well as of the adjoining 
States, are the siliceous ones, commonly of jasper or chert or white or grey granular silica 
finely interbanded with magnetite or haematite, the whole being usually more or less crumpled, 
or brecciate, and standing nearly vertical. The unchanged iron range rock seldom carries 
iron enough to be an ore, and contains usually below 35 per cent. On the other hand the 
secondary ore bodies, chiefly hmmatite or limonite, formed in troughs of the underlying schists 
or eruptives, are often of excellent quality. 
At present the Helen mine at Michipicoton is the only one working a deposit of this 
sort. The siliceous iron range rocks occur in practically every Lower Huronian area in 
Ontario, and have been traced, excepting a few important breaks, right across the northern 
half of the province. An examination of these was made during last summer by Professor 
Coleman, 
Port Arthur. — Banded jaspery ores of low grade have been long known to exist along 
Mattawin River and on Hunters Island, the latter including the N.W. extension of the 
famous vermillion iron range of Minnesota. The nearest exposures to Port Arthur are in the 
neighbourhood of Kaministiquia station C.P. R. One occurs about a mile south of the station, 
and here red jasper is interbanded with hmmatite and magnetite. The strike is about east 
and west and the dip almost vertical. The other outcrops are on the west side of Kaminis- 
tiquia river. South of Coumee township, iron deposits containing bands of magnetite one or 
two feet wide have been traced for a distance of eight miles. 
To the north of Atikokan River a little above Sabawe Lake, the range is disclosed as a 
steep narrow hill of green schist interbedded with lenses of magnetite. A tunnel 288 feet 
long has been driven into the ridge a little above its base and shows the following section — 
rock, pyrrhotite and ore 70 feet, ore 44 feet, rock 62 feet, ore 10 feet, rock 21 feet, ore 16 
feet, rock 65 feet, total 288 feet. These large lenses of magnetite stand nearly vertical and 
run in a direction almost east to west. Several diamond drill holes have also been made at 
different angles which prove that these deposits extend for a considerable distance and 
maintain their dimensions. The rocks probably belong to the Keewatin or Lower Huronian 
system. Gold also has been found in this district. 
On the south side of Nickel Lake in Watten township, the iron range consists principally 
of granular silica interbanded occasionally with magnetite, but more often heavily charged 
with sulphides, especially pyrrhotite. In places the sulphides become massive, hardly 
anything else being present, and one band of pyrites 15 feet thick just at the shore of Lake 
Nickel may, in future, be of importance as a source of sulphur. North of the lake there are 
two ridges containing much banded quartz and magnetite ; none, however, of the iron range 
deposits examined in this district can be called marketable ore, but there are indications that 
secondary ore deposits may exist, and a lens-shaped deposit of magnetite 24 feet wide and 
270 feet long has been found near the junction of a ridge of granite with a mass of green schist, 
in the neighbourhood of Watten township. 
Banded iron ores have long been known to exist on the Slate Islands, which lie at a 
distance of eight miles from the’ shore in Lake Superior. As .the shipping facilities are 
unsurpassed, the discovery of workable deposits would be of great importance. The group 
consists of one large island, a smaller one and a number of islets. The islands to the north 
consist chiefly of volcanic and schistose rocks ; banded jasper and conglomerates occur, but no 
deposits of iron were found. 
At the Helen Mine (Imp. Inst. Journ., Vol. vil., p. 125) several drill holes have been 
put down, and analyses made of the cores at different depths. Drill hole No. r, located near 
the point, was sunk vertically 188 feet, all in ore, containing on the average 63*89 p.c. of iron 
