Uses of Mineralogy.
Professor Tennant states there have been already described 500 minerals, more than half which number are found in the British Isles; whilst more than 450 are found in our colonies. In the International Exhibition of 1862, our vast colonial mineral wealth was shown in remarkable specimens of gold, silver, copper, precious stones, &c., many of which had been found by working miners who had been sent out from this country. Yet, miners are generally ignorant of the value of minerals, which they reject as not worth collection: now, the gold they collect is worth 4l. per ounce; but rough stones are often rejected, which are worth 50l. per ounce, and some 500l. per ounce—they are diamonds. Mr. Tennant believes that, in many of our colonies, these minerals are thrown away, whereas a little knowledge of the use of the blowpipe would enable miners to distinguish one substance from another.
Our Coal Resources.—The Deepest Mine.
Professor Morris describes the carboniferous series of rocks in England which contain Coal as deposited above the old red sandstone, or what have been called the Devonian rocks, and several thousand feet in thickness, though the coal measures are of much more limited depth, and the mines of coal vary from thirty feet to only two inches thick. The distribution of Coal in England is much greater than in any country in Europe; though in the United States of America, near Pittsburg, the beds of coal extend over a vast area, and one is of great thickness. The quantity of coal that is raised from the pits in this country, however, exceeds that from all the other coal-fields in the world.[14] The probable duration of coal in England has formed an interesting subject of speculation with some geologists, who have estimated the period variously at from 300 to 1000 years. Sir William Armstrong, at the Meeting of the British Association, in 1863, estimated the minimum period of the northern coal-field at 200 years; but Mr. N. Wood, the great coal-viewer of the North, is of opinion that of the northern coal-field no conjecture, of practical utility, can yet be formed, as more than one half of the basin, lying under the sea, has not yet been explored.
Sir William Armstrong’s remark, however, was misunderstood, and thought to refer to the coal supply of the whole kingdom, whereas he limited the remark to the coal-field of Durham and Northumberland. This misapprehension re-opened the question of the exhaustion of our coal resources, and led to the communication of some valuable evidence to the Times journal. Thus, Mr. E. Hull, of the Geological Survey, states as the result of a series of investigations of the British coal-fields, that adopting the limit of depth at 4000 feet, he found there to be enough workable coal, at the rate of consumption for that year, (about 71,000,000 tons,) for nearly 1000 years; and even if the consumption should ultimately reach 100,000,000 of tons, that supply could be maintained for 700 or 800 years.
With respect to the assumed depth, 4000 feet, Mr. Hull adds:
“Already a depth of nearly 1000 yards has been reached in a Belgian colliery, and coal is now being extracted from depths of 700 and 800 yards in Lancashire. Even with the vertical limit of 4000 feet, I have since found reason to believe that the estimate I arrived at in the case of the South Wales coal-field was rather under than over the truth. In that coal-basin alone, with an area of 906 square miles, I calculated that the rate of consumption for 1859, of 9½ millions of tons, could be maintained for 1600 years; but it is only right to state, that Mr. H. Vivian, M.P., in a pamphlet published by him in 1861, controverts this view, and arrives at the conclusion that ‘South Wales could supply all England with coal for 500 years, and her own consumption for 5000.’
“As regards the absolute quantity of mineral fuel in this island, it may be considered as practically inexhaustible. The seams of coal outcrop in our coal-fields, and descend under the Permian and Triassic formations to depths exceeding 10,000 feet. The question of the available supply is therefore one depending on the rapidity of production and the limit of depth.”
Dr. Buckland, in 1841, dwelt upon the wanton waste of coal at the pits, which, in 1836, he had maintained would finally “exhaust the Newcastle coal-field at a period earlier by at least one-third than that to which it would last if wisely economized.” The waste has, however, been much abated.