SCIENTIFIC SUMMARY. 
125 
tations. Rails of this description were laid down last year on the London 
and North-Western line, parallel with the very best iron forms, and such 
was the durability of the former, that they exhibited very little appearance 
of wear, whilst the latter had on several occasions to be renewed. The 
result of this experiment has been to show the directors the advantage of 
the steel over the iron rails ; and we find that they — having agreed with 
Mr. Bessemer in connection with the royalty, &e. — have arranged for the 
production, at Crewe, of 10,000 tons per annum of the new form of rail. — 
Vide The Mining and Smelling Magazine , for September. 
Reports of the Inspectors of Coal Mines . — These have just been published, 
and it is unsatisfactory to observe that whilst the deaths in 18G1 amounted 
to only 943, they rose in 1862 to the alarming number of 1,133. It seems 
that nearly all the fatal and non-fatal explosion cases which occurred in 
the Yorkshire mines during the past year, were attributable to the im- 
proper employment of candles for lighting the mines, and of gunpowder 
for blasting purposes. A strange accident befel a man in one of the Nor- 
manton mines : he had a good and well-locked safety-lamp by him, but 
while working in a certain locality, his pick, in meeting a brass-lump, 
produced a few bright sparks, which igniting some fire-damp, he was 
immediately scorched. 
Exports of Iron from the British Isles.- — It is with much pleasure that 
we record a very great increase in the value of iron exported during the 
six months ending June last, over the corresponding six months of the 
previous year. From the Board of Trade returns which have been quite 
recently issued, we perceive that, even after deducting the decrease of 
£4,087 in the value of “ old iron ” exported this year, there is still left the 
very large surplus of £756,894 in the value of the other varieties — pig, 
bar, railroad, cast, wrought, old, steel, &c. 
Silver in Copper Mines. — It is not generally known that in the copper 
mines of Lake Superior, silver is found in the greatest purity, forming 
veins which traverse the native copper, or existing in forms which have 
not inaptly been compared with the trunks of trees. “ Its varied forms, 
and its extreme purity, although in conjunction with the copper, render 
it a subject of the greatest curiosity, both metals having been, some think, 
subjected to a heat that must have been equal to a refiner’s smelting heat ; 
and yet the metals are each found in perfect purity.” — ( The Geologist , 
vol. vi. p. 69.) 
MINERALOGY. 
Intimate Structure of Minerals. — Dr. Zirkel has submitted numerous 
thin sections of various rocks to microscopical examination ; occasionally 
employing a magnifying power of 2,000. The following results have been 
arrived at : — The quartz entering into the composition of granites, 
porphyries, and trachytes, exhibits several minute cavities which, under 
the highest powers employed, appeared as minute points. Small black 
acicular crystals project from the sides of the vitreous cavities, which, 
moreover, contain a vesicle. Several empty spaces may also be observed, 
and owe their existence to the development of gaseous matters. The 
quartz in all forms of granite includes thousands of crystals of vitreous 
