138 Chronicles of Scrence. | Jan. 
In addition to these, of ores of the metals, our mines give us 
Silver, Nickel, Cobalt, Tungsten, Antimony, Manganese, and others. 
Of earthy minerals we produce Barytes, Strontian, and Gypsum, in- 
dependently of the Lime, Magnesia, Porcelain, and other clays; while 
the Salt districts of Cheshire and Worcestershire give us above 900,000 
tons of Salt annually. 
Gold must be regarded as an unusual product from British rocks, 
but the Quartz lodes in the vicinity of Dolgelly gave us of that precious 
metal, in 1861, 2,784 standard ounces, of the value of 10,817/., and in 
1862, 5,299 standard ounces, the value of which was 30,3901. 
Nearly all the Lead ores of these Islands contain Silver, and from 
this source, by an interesting Metallurgical process, we obtaimed, in 
1861, 569,530 ounces, and in 1862, 686,123 ounces of sterling Silver. 
From the returns obtained by the ‘Mining Record’ Office, we 
learn that the values of the Metals produced from the ores of the 
British Islands alone, and Coals, were at the place of production— 
In 1861 at 34,602,853. 
In 1862 at 54,691,037. 
In this rapid sketch, we endeavour to convey a correct idea of the 
importance of our Mining operations, without loading our pages with 
details, which may be consulted by all who are interested in the sub- 
ject, in the publication already quoted. 
Directly connected with our Coal-Mining, one question of the 
highest importance has been recently revived :—that is, the probable 
duration of our coal-beds. Sir William Armstrong, in his Address as 
President of the British Association, at the recent Meeting at New- 
castle-on-Tyne, spoke as follows on this subjeet :—‘‘ By combining 
the known thickness of the various workable seams of coal, and com- 
puting the area of the surfsce under which they lie, it is easy to arrive 
at an estimate of the total quantity comprised in our coal-bearing 
strata. Assuming 4,000 feet as the greatest depth at which it will 
ever be possible to carry on mining operations, and rejecting all seams 
of less than two fect in thickness, the entire available coal existing in 
these Islands has been calculated to amount to about 80,000 millions 
of tons, which, at the present rate of consumption, would be exhausted 
in 930 years; but, with a continued yearly increase of two millions 
and three quarters of tons, would only last two hundred and twelve 
years.” * 
Mr. Greenwell stated a few years since his opinion that “the 
Northern coal-field would continue 331 years.” Mr. T. Y. Hall 
agrees in the main with Mr. Greenwell, and taking the annual con- 
sumption of the Newcastle coal-field at 14 millions of tons, he gives 
365 years as the period at which this coal-field will be exhausted. 
Mr. Fordyce in 1860, supposing the drain upon this coal-field to be 
20 millions of tons annually, says, “then at this rate of demand the 
coal-field would be exhausted in the course of 256.years.” + 
* Report of the Meeting of the British Association at Newcastle, 1863. 
+ See ‘The Transactions of the North of England Institute of Mining En- 
gineers,’ and Fordyce’s ‘ History of Coal, Coke, and Coal Fields,’ 1860. 
