NOTES AND QUERIES. 
235 
iniproliable they might be aiTested and hekl in a chink or cavity in the gravel. As our 
correspondent's notice now reads, he would seem to state they were solidly embedded iu 
the matrix of the gravel at a depth of thirty-five feet, a by no means likely occurrence. — 
Ed. Geol.] 
Production of Coppee. — The following extracts are from tlie ' Lake 
Superior Miner : ' — 
" In 1830, the total production of the copper mines of the world was 
about 25,500 tons of metal, and of this amount Great Britain produced 
13,200, or more than 50 per cent, of the whole, while the United States 
and Canada furnished but 50 tons, or two-tenths of 1 per cent. The Russian 
Empire then produced nearly 4000 tons, the Austrian Empire 2150 tons, 
the whole of Asia some "2500 tons. In 1853, twenty-three years later, 
Britain had only increased her annual product to 14,500 tons, her per- 
centage of the whole amount receding to 26 ; while Chili, in South Ame- 
rica, which in 1830 onl}^ yielded 200 tons, had raised her product to 14,000 
tons, or over 25 per cent, of the total production. From that period for- 
ward to the present time, the copper production of the Chilian mines we 
believe, exceeded those of any other country, the value of their exports in 
that metal alone amounting to -8 10,760,000 in 1857, while the value of 
British mine products for the same year was worth about 89,500,000. 
The liussians had increased the yield of their mines to 6,500 tons, or llf 
per cent, of the whole ; the Austrians to 3300 tons, or 6 per cent. ; the 
whole of Asia only 3000 tons, or 5^ per cent. ; while the United States 
and Canadas raised that year 2000 tons, over 3| per cent, of the total pro- 
ducts for that year, which were about 55,700 tons ; Australia and New 
Zealand produced about 3(X)0 tons ; Cuba, 350 tons ; Scandinavia, 2000 
tons ; the German States, 1450 tons ; and the rest of Europe, exclusive of 
the countries above named, 1000 tons. 
" During the past ten years, the mines of Lake Superior have probably 
increased their production more rapidly than those of any other country, 
the exports for 1861 — 7500 tons of metal — being about twelve times greater 
than those of 1851. That our ratio of increase in the coming ten years 
will be as great should not probably be expected, as that would amount to 
90,000 tons ; more by at least 40 per cent, than the present product of the 
world's mines. Of tlie 80 miles of copper range east of us, and 40 to 50 
miles west, comparatively few mining properties have yet been explored." 
Usefulness of Diamonds. — Many persons suppose that diamonds are 
only used as jewellery, — for rings and other articles of personal adornment, 
— and that they are really of no essential value whatever in the practical arts. 
This is a mistaken notion ; they are used for a great number of purposes in 
the arts. Thus, for cutting the glass of our windows into proper sizes, no 
other substance can equal it, and it is exclusively used for this purpose. 
A natural edge, or point, as it is called, is used for this work, and thousands 
are annually required in our glass factories. Diamond-points are also 
employed for engraving on carnelians, amethysts, and other brilliants, and 
for the finer cuttings on cameos and seals. Being very hard, the diamond 
it also used in chronometers for the steps of pivots ; and as it possesses 
high refractive power and little longitudinal aberration, it has been success- 
fully employed for the small deep lenses of single microscopes. The niag- 
nifj'ing power of the diamond in proportion to that of plate glass, ground 
to a similar form, is as eight to three. For drawing minute lines on hard 
steel and glass, to make micrometers, there is no substitute for the diamond 
point. The rough diamond is called " bort," and the " points " used for glass 
cutting are fragments of the borts. Great care and skill are necessary in 
selecting the cutting-points^, because the diamond that cuts the glass most 
