SCIENTIFIC SUMMARY. 
439 
mines, gradually displacing those of iron wire, which, to have the same 
strength, require to be very much thicker and therefore heavier than 
those of steel. 
Sulphuretted Hydrogen in the Reduction of Copper. — It has been discovered 
that this gas may be prepared in large quantities, from the ignition of 
pyrites under certain conditions. The process is now adopted in Norway, 
and applied to the separation of copper from poor cupriferous pyrites. 
Copper Ore in Cheshire. — At Alderley Edge, is a very singular deposit of 
copper ore which has impregnated sandstone. Although the percentage 
of copper in the sandstone is not more than lj, yet, by the methods of 
reduction practised, the copper is separated with profit on an extensive 
scale. The average yield of the mines is 25 tons of copper precipitate 
monthly ; and the profits have reached to some thousands of pounds 
yearly. Mr. George Henwood, who lately inspected the works, describes 
the process adopted. It consists in grinding the stone, and then sub- 
mitting it to the action of hydrochloric acid for eighteen or twenty-four 
hours, when all the copper will be extracted and the sand made perfectly 
white. The liquor is drained off, and scrap iron placed therein, which 
soon precipitates all the copper, the precipitate is washed and dried, and 
is then ready for the market. 
MININCt. 
Mineral Statistics.- — In the paper of Mr. Robert Hunt, already referred 
to, we find various statistics of the mineral products of the United Kingdom 
for 1861. They have also appeared in a separate form. 
Number of collieries 3,052 
Quantity of coal raised 83,635,214 tons 
Value £20,908,803 
Lives lost annually in coal mines ... about 1,000 
In the ten years ending 1860 the number of lives lost was 9,090. 
Total valueof metals produced from British minerals in 1861... £13,693,550 
Coals 20,908,803 
Total value of mineral produce £34,602,353 
Amongst the metals, gold appears for the first time to the extent of 
£10,816, being the production of the Merionethshire mines. 
The value of the silver extracted from lead ore raised in the United 
Kingdom in 1861, was £144,161. 
In Great Britain there are 336,000 persons actually engaged in mining 
operations, exclusive of those in quarries of all kinds. Of these 250,000 
are coal miners. Probably not more than 300 of the whole number are 
receiving any such course of instruction as is necessary to fit them for the 
labours for which they are destined. 
Boring by Diamonds. — Some time since it was suggested that black or 
rough diamonds might be employed for the perforation of hard rocks. 
This suggestion has been put into practice by a French engineer, M. 
