JUVENILE LECTURES.

The usual short course of lectures adapted for a juvenile audience will be delivered on Wednesday afternoons, January 6th and 13th, at 5 o'clock, by ERIC STUART BRUCE, M.A., on "Navigation of the Air."

Special tickets are required for these lectures, which can be obtained on application to the Secretary. A sufficient number of tickets to fill the room will be issued to members in the order in which applications are received, and the issue will then be discontinued. Subject to these conditions each member is entitled to a ticket admitting two children and an adult. The supply is now nearly exhausted, so members requiring tickets should apply at

expected in the near future. It has been sug-. gested that a similar course of lectures dealing with the supplies of the non-metallic minerals of economic importance would be of interest. The subject is undoubtedly one of great importance from a commercial point of view, as will be evident from a moment's consideration of the enormous value of the resources of nonmetallic minerals. In the United Kingdom alone the value of the non-metallic minerals raised in 1901 was £111,000,000, while in the United States it was 113,000,000. In both cases it was considerably greater than the value of the metallic products. Moreover, with the advancement of science and techno-. logy, attention is constantly being devoted to new raw materials. Thus pitch-blende, the only mineral in which uranium occurs in appreciable quantities, serves for the production of a yellowish-green fluorescent glass, and is now eagerly sought for as the source of radium. Monazite, a silicate containing rare earths, was merely a scientific curiosity, until Auer von Welsbach introduced the incandescent

mantle for gas lighting. Calcite is now required for the polarisation apparatus for the sugar industry, mica in the electric industry, magnesite for lining open-hearth steel furnaces, china clay in paper manufacture, and phosphates as fluxes in iron smelting with the object of obtaining highly phosphatic slags for use in agriculture. These are a few examples of the constantly increasing field of usefulness for non-metallic minerals. The most important of all these are the combustible minerals, the coals and bitumens, with which I propose to deal this evening.

productive. In America, the chief deposits of commercial value are in the State of New York. At Hague, Warren County, New York, the bed of graphite (Fig. 1) is nine feet thick and is formed of alternating layers of highly graphitic sandy shale and schist.

The purest varieties of graphite are used in the manufacture of pencils and as lubricants; the crystalline (Ceylon, Passau, Scandinavia) for crucibles, stove blacking, paints, and foundry facings. Artificial graphite now enters into competition with the natural product. The manufacture of artificial graphite, started at Niagara Falls a few years ago, continues to increase in importance. In 1901 there were made 1,125 tons, valued at £2 a ton. Half this output was used for the manufacture of electrodes.

Coal. The word coal is a popular rather than a scientific term, being applied not only to beds of fossilised vegetation, but to any mineral substance capable of being used as fuel. The world's production of the various varieties of coal in 1901 exceeded 789,000,000 tons. It is difficult to realise what this vast amount means. Imagine it placed in 10-ton waggons along a railway line; the train would be 426,000 miles long. It would have to go seventeen times round the equator in order to hold a year's production of coal. The production of the various countries in follows:

1901 was as

GRAPHITE MINE NEAR HAGUE, NEW YORK. (C. D. Walcott.)

coarse-grained best variety. Most of the Ceylon graphite contains more than 90 per cent. of carbon, whilst not more than a quarter of the Austrian output reaches that degree of purity. Of the districts of subordinate importance Piedmont in Italy and Passau in Bavaria are the most productive. The celebrated Borrowdale mines in Cumberland and the Alibert mine in Siberia have long ceased to be

Kingdom, 227,095,000 tons, and Germany, 107,436,000 tons. The production per head of population in the three countries was three and one-third tons, five and a-half tons, and two tons respectively.

Anthracite.-Anthracite is regarded as a coal, from which all the gas has been removed. It is hard, brittle, and lustrous, and burns with little flame and no smoke. Like other coals it occurs in beds usually of carboniferous age. The principal anthracite regions are in Eastern Pennsylvania and in South Wales, to the west of the Vale of Neath. The present annual output of these two regions is 50,000,000 and 2,000,000 tons respectively.

Bituminous Coal. This term, a misleading one, is applied to coal which burns with a more or less smoky flame, and chemically occupies a place between brown coal and anthracite.

This field furnishes 66.7 per cent. of the total production of the United States. Next in importance are the portions of Illinois, Indiana, and Kentucky, which make up the central coalfield. This contributed 16.6 per cent. of the total output. The western coalfield furnished 8.7 per cent, the Rocky Mountain, 6.2 per cent., and the Pacific Coast, 12 per cent. In Germany, the Rhenish-Westphalian coalfield is the most extensive, whilst the largest in Europe is the Donetz coalfield in Russia.

The future of British coal mining is a matter for serious consideration. In 1840, Great Britain produced 75 per cent. of the world's supply of coal; at the present time it produces only 28 per cent. The condition of the iron trade has always exercised a most important influence on the production of coal, so that a large demand for iron draws with it a large

"Flaming" was suggested by Percy as a good substitute for the word bituminous. For economic purposes he classed bituminous coals as (1) non-caking or free-burning, rich in oxygen, (2) caking, and (3) non-caking, rich in carbon. Gruner's researches led to the following classification :—

The passage from one class to another is gradual. The ash-forming constituents of coal vary from 0.5 to 30 per cent. Cannel coal is a variety of bituminous coal, rich in hydrogen, especially valuable as a gas coal. Coal is mined in the United Kingdom from beds of carboniferous age. The seams worked vary from 11 inches up to 30 feet in thickness. The great coal counties are Durham, Yorkshire, and Glamorganshire. Information regarding the occurrence of coal in Great Britain is given in E. Hull's "Coalfields of Great Britain." In the United States the most important coalfields are those contained in the Appalachian mountain system, which extends from Pennsylvania and Ohio, to Alabama.

demand for mineral fuel. Statistics show, however, that since 1870 the world's production of pig iron has increased from 12,000,000 to 44,000,000 tons in 1902, but the share of Great Britain has fallen from 48.8 per cent. to 20 per cent. It cannot be denied that during the past quarter of a century its coal-mining industry has not developed so rapidly as that of its American and German commercial rivals. Great Britain, until 1899, held the first place.

It is interesting to note that, although coal was first mined as far back as the year 1113, by the monks of the Klosterrath Abbey at Kirchrath on the Wurm, it was in Great Britain that it was first used on a large scale, on the Tyne, the "coaly Tine" of Milton. In 1239, King Henry III. is said to have granted a charter to the townsmen of Newcastle-onTyne, for the raising of coal for fuel, and so early was their produce attracted to London, that by the beginning of the next century great complaint arose of the injury done by the coal

smoke to the health of the citizens. "The nice dames of London," says Stow, in 1598, "would not come into any house or room where sea-coals were burned." By the time of Charles I, the use of coal had become very general, and as the demand increased the price went up. In 1643, a pamphlet was published with the imprint "Printed in the year that sea-coal was exceeding dear." At the beginning of the 19th century, about 10,000,000 tons were raised annually in Great Britain. The continental production at that time was very small, the large expanse of forest land having delayed the necessity for turning to mineral fuel. Since then enormous strides have been made. At that period the machinery was of a primitive type. Even in 1837 a colliery was in operation in the county of Durham at which coals were raised by a donkey and banked out and sold by an old woman. Compare this. with a modern pit raising 2,000 tons a day from a depth of a quarter of a mile. At Bolsover colliery 3,217 tons have been raised from a depth of 1,175 feet in nine hours, and a week's record at the Cambrian colliery, Clydach Vale, was 13,019 tons, raised from a depth of 1,350 feet. The literature of coal mining is so extensive that it is unnecessary here to enter into details of the remarkable improvement in the mechanical appliances used at collieries. Illustrations will be found in abundance in the standard work by Mr. Herbert W. Hughes, who gives some remarkable photographs taken by himself underground, showing the methods of mining in the 10-yard coal of South Staffordshire. Some very striking examples of machinery were shown in the mining building at Düsseldorf Exhibition last year. Among these must be mentioned the colossal winding engine built by the Prince Rudolph Ironworks at Dülmen for the Preussen colliery of the Harpener Company. It is a vertical 800 horsepower engine, designed by Tomson, to wind from a depth of 4,000 feet, and has two conical spiral drums 32 feet in greatest diameter and 11 feet wide. The drums are not, as is the usual practice, placed side by side, but one behind the other, an arrangement that increases the safety and lessens the wear of the rope. Whilst for this engine, which created amazement by its vast size, steam was used as motive power, there was in the same building an electrically driven winding engine, made by the Friedrich Wilhelm works, of Mülheim, which showed that electric driving may now be applied with advantage on a large scale,

This engine, built for the Gelsenkirchen Company, raises 1,000 tons in six hours from a depth of 1,650 feet. The two electromotors are each of 1,400 horse-power. The absence of a winding drum is due to the fact that the Koepe system of winding with only one rope is employed. An interesting model showed the winding and coal-washing plant of the Emscher shaft of the Kölner Company. There was also shown a Riedler express pump with double acting plungers of 7 inch diameter and 9.8 inch stroke, making 200 revolutions per minute, and raising in that time 550 gallons of water from a depth of 1,970 feet. It was driven by an alternating motor made by the Helios Electricity Company of Cologne.

With the rapid rate of consumption, anxiety as to the duration of the British coalfields is well founded. Professor Hull estimates that the total quantity of coal within a depth of 4,000 feet still remaining is 81,683,000,000 tons. This estimate is reassuring, although it is not in accord with the less optimistic and divergent views on the question expressed by Professor Stanley Jevons, by the Right Honourable Leonard H. Courtney, by Mr. R. Price-Williams, by Mr. T. Forster Brown,* and by Lieut. C. W. Bellairs.† All these estimates are of slight value, owing to the impossibility of prophesying either the rate of increase in production and consumption, or the limits at which mining may be carried on with profit. Early in the last century, a shaft 100 feet in depth was an object of wonder, and a glance over the history of the depths hitherto attained, clearly shows the remarkably rapid progress that has been made in this respect. At the present time the greatest depth at which mining operations are carried on in Great Britain has been reached at the Pendleton colliery, near Manchester, where the deepest workings are nearly 3,500 feet below the surface. This enormous depth has, however, been exceeded in other countries, notably in the Lake Superior district, where the Red Jacket shaft of the Calumet and Hecla copper mine has now attained the record depth of 4,900 feet, and in Belgium, where a colliery at Mons is 3,937 feet deep. Depths such as these show that the limit of depth of 4,000 feet adopted by Professor Hull and by the Royal Coal Commissioners in 1870, though ridiculed at the time, was well within the

Journal of the Society of Arts, vol. 47, p. 506. + Ibid, vol. 49, p. 549.

"Mining at Great Depths." By Bennett H. Brough. Journal of the Society of Arts, vol. 45, p. 57.

bounds of possibility. In view of the marvellous efficiency of modern winding engines, no considerations of a mechanical nature need limit the prospective depths of shafts. By far the most important obstacle to very deep mining is the certain and proportionate increase of temperature according to depth. At the Paruschowitz borehole, in Silesia, the deepest in the world, put down by the Prussian Government to a depth of 6,573 feet, this increase of temperature with depth has been found to be 1° Fahrenheit for 62.1 feet. Taking this as a fair average, a coal seam at a depth of 4,000 feet would be, without the cooling action of an artificial ventilating current, 64° warmer than ground near the surface. Further information on these questions may be expected from the labours of the Royal Commission appointed, with terms of reference of a far-reaching character, on December 28, 1901. On August 5, 1903, they issued an interim report, offering no opinion nor recommendation, but containing much valuable evidence.

The questions of the possible economies in the use of coal and of the adoption of better methods of working should prove the most fruitful field for the labours of the Commission. In Great Britain more and more attention is being devoted to improvements in details of mining. Although the use of mechanical coal cutters has by no means become as general as it has in the United States, where 25 per cent. of the output is thus obtained, there has recently been a distinct increase in the use of these labour-saving appliances. Moreover, endeavours are being made to economise in the consumption of coal, notably in the South Staffordshire coalfield, where the producer-gas invented by Dr. Ludwig Mond, has recently been introduced as a cheap source of heat and power. That great economies in the home consumption of coal have been effected since 1871 is unquestionable. Indeed, Mr. Price-Williams has shown that, whereas in 1871 the iron and steel trade required 30 per cent. of the coal consumed in the United Kingdom, its requirements had been reduced to 16 per cent. at the time he read his paper before the Statistical Society in 1889. With improvements conducive to economy in fuel it is evident that a considerable industrial development may take place with a very slight increase in coal consumption.

From time to time important new discoveries of coal are made in various parts of the world. Coal, for example, has now been struck at Dover in the area described by Mr, W.

Whitaker. In Belgium again, in that portion of the province of Antwerp known as the Campine, coal of excellent quality has recently been found, and it is estimated that this new field contains more than 500,000,000 tons of coal. In the British colonies and dependencies the production of coal increases year by year. In the eastern states of Australia there are some 62,000 square miles of coal-bearing country, and the coal resources of India have been shown by Professor W. R. Dunstant to be enormous. There can, therefore, be no doubt that there are ample resources to meet all the demands for coal. Nevertheless, with a view to husbanding the British coal resources, the need for taking measures to avoid waste in mining is apparent. The great waste of small coal, though lessening year by year, is still a reprehensible extravagance. The more general use of coal-mining machines would tend to reduce this source of waste by furnishing a larger proportion of lump coal. There is, too, much needless waste in the consumption of coal, notably in the coal used for domestic purposes. Saving in this direction might give the country years of prosperity.

Brown Coal.-Under the general term of lignite or brown coal, Percy included those varieties of coal that form the intermediate stage between peat and true coals of carboniferous age. According to their geological age, brown coals have a distinct ligneous texture (true lignite, fibrous brown coal), or are without organic structure (earthy brown coal), or black and lustrous with conchoidal fracture. Brown coal burns with a very long smoky flame. It is largely used for heating steam boilers, evaporating pans, and for domestic purposes. The better qualities are sometimes used in Austria and Germany for metallurgical purposes. In Great Britain, brown coal has been worked only in a seam of lower tertiary age at Bovey Tracey in Devonshire. On the Continent, brown coal is extensively mined, the greatest production being shown by NorthWest Bohemia and the district of Halle in Prussia. In 1902, Bohemia with 36,074 miners raised 18,262,592 tons of brown coal, whilst the Halle district with 35,055 miners raised 29,233,936 tons in 1902. Besides this, the mines of the Cologne district raised 5,354,440 tons, the kingdom of Saxony, 1,635,000 tons, Upper Bavaria, 24,000 tons, and Styria in Austria, 2,585,233 tons. The beds of brown

Journal of the Society of Arts, vol. 38, p. 513. +Ibid, vol. 50, p. 371.