Lectures on Popular and Scientific Subjects

Part 1

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LECTURES

POPULAR AND SCIENTIFIC SUBJECTS

BY THE

EARL OF CAITHNESS, F.R.S.

DELIVERED AT VARIOUS TIMES AND PLACES.

Second Enlarged Edition.

LONDON: TRÜBNER & CO., LUDGATE HILL. 1879.

Ballantyne Press

BALLANTYNE, HANSON AND CO.

EDINBURGH AND LONDON

CONTENTS.

COAL AND COAL MINES

SCIENCE APPLIED TO ART

A PENNY'S WORTH; OR, "TAKE CARE OF THE PENCE, AND THE POUNDS WILL TAKE CARE OF THEMSELVES"

PAST AND PRESENT MEANS OF COMMUNICATION

THE STEAM-ENGINE

ON ATTRACTION

THE OIL FROM LINSEED

HODGE-PODGE; OR, WHAT'S INTILT

LECTURES ON POPULAR AND SCIENTIFIC SUBJECTS.

COAL AND COAL-MINES.

There are few subjects of more importance, and few less known or thought about, than our coal-mines. Coal is one of our greatest blessings, and certainly one originating cause of England's greatness and wealth. It has given us a power over other nations, and vast sums of money are yearly brought to our country from abroad in exchange for the coal we send. Nearly £17,000,000 is the representative value of the coal raised every year at the pit's mouth, and £20,000,000 represent its mean value at the various places of consumption. The capital invested in our coal-mining trade, apart from the value of the mines themselves, exceeds £20,000,000 sterling, and the amount of coal annually extracted from the earth is over 70,000,000 of tons. Taking the calculation of a working miner--J. Ellwood, Moss Pit, near Whitehaven--we may state, that if 68,000,000 tons were excavated from a mining gallery 6 feet high and 12 feet wide, that gallery would be not less than 5128 miles, 1090 yards, in length; or, if this amount of coal were erected in a pyramid, its square base would extend over 40 acres, and the height would be 3356 feet.

There are grounds for believing that the produce of the various coal-fields of the world does not at present much exceed 100,000,000 of tons annually, and therefore our own country contributes more than three-fifths of the total amount. If we divide the coal-yielding counties of Britain into four classes, so as to make nearly equal amounts of produce, we find that Durham and Northumberland yield rather more every year than seven other counties, including Yorkshire. Derbyshire, again, produces more than eight other counties, and nearly as much as the whole of North and South Wales, Scotland, and Ireland--the yield of the latter being about 17,000,000 of tons, and that of the two first-named about 16,000,000 of tons.

In 1773 there were only 13 collieries on the Tyne, and these had increased to upwards of 30 in 1800. The number of collieries in 1828 had increased to 41 on the Tyne, and 18 on the Wear, in all 59, producing 5,887,552 tons of coal. The out-put of coal in Northumberland and Durham in 1854 was no less than 15,420,615 tons, and now in these two counties there are 283 collieries. Mining began on the Tyne and continued on the Wear, where the industry has been largely developed. There are in all about 57 different seams in the Great Northern coal-field, varying in thickness from 1 inch to 5 feet 5 inches and 6 feet, and these seams comprise an aggregate of nearly 76 feet of coal. Taking the area of this field to be 750 square miles--a most probable estimate--we may classify the contents as household coal, steam coal, or those employed in steam-engine boilers, and coking coal, employed for making coke and gas. Of household coal there is only 96 square miles out of the total 750, all the remainder being steam or coking and gas coal. The greater part even of this 96 square miles has been worked out on the Tyne, and the supply is rapidly decreasing also on the Wear, where the largest bulk of the household coal lies. The collieries of the Tees possess but six square miles out of the 96, as far as we at present know. Turning, however, to that part of the coal-field regarded as precarious, and consisting of first, second, and third-rate household coal, we have for future use 300 square miles. London was formerly supplied from the pits east of Tyne Bridge, where is the famous Wallsend Colliery, which gave the name to the best coal. That mine is now drowned out, and, like the great Roman Wall, at the termination of which it was sunk, and from which it derived its name, is now an antiquity. There is now no Wallsend coal, and the principal part of the present so-called coal comes from the Wear, but the seam which supplied that famous pit is continued into Durham, and that seam, or its equivalent, sends a million or two of tons every year into London. The supply, however, in this district is rapidly decreasing. Careful calculations have been made as to the probable duration of this coal, of which the following is a summary. The workable quantity of coal remaining in the ten principal seams of this coal-field is estimated at 1,876,848,756 Newcastle chaldrons (each 35 cwt.). Deducting losses and underground and surface waste, the total merchantable round or good-sized coal will be 1,251,232,507 Newcastle chaldrons. Proceeding on this estimate, formed by Mr. Grunwith in 1846, we may arrive at the probable duration of the supplies: taking the future annual average of coal raised from these seams to be 10,000,000 of tons--and this is under the present rate--the whole will be exhausted in 331 years. A still later estimate was made by Mr. T.G. Hall in 1854, and he reckoned the quantity of coal left for future use at 5,121,888,956 tons; dividing this by 14,000,000 of tons as the annual consumption, the result would be 365 years; and should the annual demand arrive at 20,000,000 of tons, the future supply of this famous coal-field would continue for 256 years. The total available coal (1871) in the British coal-fields, at depths not exceeding 4000 feet, and in seams not less than 1 foot thick, is 90,207,285,398 tons, and taking into account seams which may yet become available, lying under the Permian, New Red Sandstone, and other superincumbent strata, this estimate is increased to 146,480,000,000 of tons. This quantity, at the present annual rate of production throughout the country--namely, 123,500,000 tons--would last 1186 years. Other estimates of various kinds relative to our coal supply have been put forth: some have asserted that, owing to increasing population and increasing consumption in manufactures, it will be exhausted in 100 years, and between this extreme and that of 1186 years there are many other conjectures and estimates.

In the United States there are about 120,000 square miles underlaid by known workable coal-beds, besides what yet remains to be discovered; while on the cliffs of Nova Scotia the coal-seams can be seen one over the other for many hundred feet, and showing how the coal was originally formed. With this immense stock of fuel in the cellars of the earth, it seems evident that we need not trouble our minds or be anxious as to the duration of our coal supply. Besides, the conversion of vegetable matter into coal seems to be going on even now. In the United States there are peat-bogs of considerable extent, in which a substance exactly resembling cannel coal has been found; and in some of the Irish peat-beds, as also in the North of Scotland, a similar substance has been discovered, of a very inflammable nature, resembling coal.

Yes! what could have produced this singular-looking, black, inflammable rock? How many times was this question asked before Science could return an answer? This she can now do with confidence. Coal was once growing vegetable matter. On the surface of the shale, immediately above the coal, you will find innumerable impressions of leaves and branches, as perfect as artist ever drew. But how could this vegetable matter ever accumulate in such masses as to make beds of coal of such vast extent, some not less than 30 feet thick? It would take 10 or 12 feet of green vegetable matter to make 1 foot of solid coal. Let us transport ourselves to the carboniferous times, and see the condition of the earth, and this may assist us to answer the question. Stand on this rocky eminence and behold that sea of verdure, whose gigantic waves roll in the greenest of billows to the verge of the horizon--that is a carboniferous forest. Mark that steamy cloud floating over it, an indication of the great evaporation constantly proceeding. The scent of the morning air is like that of a greenhouse; and well it may be, for the land of the globe is a mighty hothouse--the crust of the earth is still thin, and its internal heat makes a tropical climate everywhere, unchecked by winter's cold, thus forcing plants to a most luxurious growth.

Descend, and let us wander through this forest and examine it more closely. What strange trees are here! No oaks, no elms, or ash, or chestnut--no trees that we ever saw before. It looks as if the plants of a boggy meadow had shot up in a single night to a height of 60 or 70 feet, and we were walking among the stalks--a gigantic meadow of ferns, reeds, grasses, and club-mosses. A million columns rise, so thick at the top that they make twilight at mid-day, and their trunks are so close together we can scarcely edge our way between them, whilst the ground is carpeted with trailing plants completely interwoven. What strange trees they are! Beneath us lies an accumulation of vegetable matter more than 200 feet in thickness--the result of the growth and decay of plants in this swamp for centuries. All things are here favourable for the growth of vegetation--the great heat of the ground causes water to rise rapidly in vapour, and this again descends in showers, supplying the plants with moisture continuously. The air contains a large proportion of carbonic acid gas, poison to animals but food to plants, which, by means of its aid, build up their woody structure. Winds at times level these gigantic plants, for their hold on the earth is feeble, and thus the mass goes on increasing.

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