SCIENTIFIC SUMMARY. 
573 
Platinum cannot be fused in graphite crucibles, as the carbon unites with 
the metal, making it very brittle. Messrs. Johnson & Matthey have pre- 
pared specimens of autogenous soldering in platinum, with tubes of the 
same, having cast iron and leaden screw joints for use with sulphuric acid 
at high temperatures. 
MINING. 
Blasting . — The Italian Minister of Public Works has reported on the 
progress of the Mont Cenis tunnel. Boring machines are now used at 
each end, worked by compressed air. In 1862, to pierce 880 metres on the 
side of Bardonneche, 45,751 holes were bored, from 75 to 80 centimetres 
(30 to 32 inches) in depth ; 72,538 borers were set to work ; there were 
54,875 blasts, and 1,334,000 cubic metres of compressed air were consumed^ 
equal to 8,004,000 cubic metres of atmospheric air. It is expected that at the 
present rate the tunnel will be completed in 12-| j^ears. In consequence 
of the many accidents from ordinary blasting, the far safer plan of blasting 
by electricity is gradually commending itself to the mining public. It has 
long been used in military mining with success, and also in civil engineering, 
where large masses of rock had to be moved, since several charges may 
be fired at precisely the same moment. Thus, a few months ago, a large 
martello tower which guarded the entrance to Chatham harbour was 
demolished. The charges of powder were each 40 lb., distributed at equal 
distances beneath the foundations ; the whole being connected by wires. 
In this kind of blasting a pair of wires, united at the extremities 
by a very fine one of platinum, is placed in the interior of the charge of 
powder. A current of electricity is passed by a magneto- electric machine. 
The wires may be of any length, and thus the workman may place himself 
out of danger. Moreover, if the charge miss fire there is no possibility of 
any smouldering spark, as in the case of the ordinary fuse, which has led 
to many accidents from this cause. 
Ventilation . — It may be remembered that at the time of the late accident 
at Risca, the ventilating power was a machine. Immediately afterwards a 
larger machine was erected ; mechanical ventilation being still preferred to 
that produced by the furnace. Lately, the machine got out of order, and 
a furnace has been erected to supersede it. English mine engineers, as a 
rule, consider furnace ventilation preferable to mechanical, whilst the 
majority of continental miners hold the opposite opinion. Mr. Rogers, of 
Farnley Wood Colliery, near Leeds, has adopted for ventilating power the 
heat of coke ovens, which may be placed either at the bottom of the upcast 
shaft, or at the surface. The system is said to work admirably ; and at 
the same time coal slack, unsaleable at Is. per ton, is converted into good 
coke worth 5s. per ton. 
Testing Air in Mines. — Mr. W. Keene, the Government examiner of coal 
fields in New South Wales, has invented a simple apparatus for estimating 
the salubrity of the'air in mines. It is a closed tin box with a glass win- 
dow in one of its sides, and containing a candle holder. A candle is lighted 
and inserted, after which the box is closed. It is then seen how long the 
candle burns ; the length of time being proportional to the amount of 
oxygen in the air examined. Thus, in a particular case, with a vessel 
