c 
1874.] Metallurgy. 263 
The peculiar conditions under which diamonds occur in the fields of South 
Africa have been well described by Mr. E. J. Dunn, who, before his recent 
return to the Cape, contributed to the Geological Society of London an inte- 
resting paper on this subje@. The so-called “dry diggings,” such as the 
well-known Colesberg Koppje and Du Toit’s Pan, are circular areas surrounded 
by horizontal shales. As to the diamond-bearing rock itself, Mr. Dunn 
describes it as an eruptive mass brought up to the surface through pipes which 
have penetrated the shales, and turned up their edges. On sinking into these 
pipes, the general sequence of deposits is—first, a few feet of sand; then, a 
layer of calcareous tufa; and this deposit passes gradually into an altered 
igneous rock, the true character of which is still an enigma. It has been sug- 
gested that it may be a gabbro or euphotide, serving as the base of a breccia 
which contains fragments of shale, dolerite, and other rocks. Can this 
euphrotide breccia be regarded as the actual mother-rock of the South-African 
diamonds ? 
METALLURGY. 
Under the head of ‘‘ Mining”’ we publish this quarter a summary of the 
‘Mineral Statistics’ for 1872, showing the quantities of ores raised in the 
United Kingdom during that year. In connection with these returns, and to 
show the position of our metallurgical industries, we may present the following 
statement, which exhibits the quantities and values of the several metals 
obtained from-the ores raised in 1872:—* 
Quantity. Value. 
EIPCITOMM sles sl ae) LOS! 6;741,929 £ 18,540,304 
BROMMEEN (Sat tu srw sijelo) Nav 7 5,703 583,232 
WIRTON en rere pTeiw, p Vicish, ie asl nf 9,560 1,459,990 
Lead Scfpicich poco an rad . 60,455 1,209,115 
SuUIVCIEE Tacit eo tenia | OZS.. 628/920 157,230 
Zine Be a) see Paves ee,  ROons 5,191 118,076 
Other metals (estimated) .. — 2,500 
£ 22,070,447 
An interesting feature is this year introduced into the ‘‘ Mineral Statistics,” 
in the shape of returns giving the consumption of coal in our blast-furnaces. 
These figures show that the quantity of coal consumed, on an average, for 
every ton of pig-iron produced, in 1872, amounted to 51 cwts. The economy 
of our iron-masters becomes evident on remembering that it was computed by 
the Royal Coal Commission that 3 tons of coal were consumed per ton of 
pig-iron. 
Mr. T. Hughes, of the Geological Survey of India, has contributed to a 
recent number of the Survey ‘‘ Records”’ some notes on the ‘ Iron-Deposits 
of Chandra in the Central Provinces,” in which he gives some interesting 
details respecting the relative amounts of ore and fuel ordinarily employed by 
the natives in their furnaces. The wealth of Chandra in iron ores is consider- 
able, and the value of the deposits is likely to be increased by the occurrence 
of coal in the neighbourhood. The native furnaces, though still liliputian, are 
larger than those commonly in use in Bengal, and several attain a height of 
nearly 6 feet. The section of the furnace is that of a cone; the hearth, as 
usual, slopes from behind forwards; the tuyeres are each g inches long, 
1} inches diameter at the larger and 2 inch at the smaller end; and the 
bellows are usually worked by hand. Taking the mean of several experiments, 
and reducing the weights to English units, we find that 8 tons of ore and 
14; tons of charcoal are consumed in the manufacture of 1 ton of wrought- 
iron by this method. 
* Mineral Statistics of the United Kingdom of Great Britain and Ireland, for the Year 1872. 
With an Appendix. By Rosert Hunt, F.R.S., Keeper of Mining Records. Longmans, 1873. 
