coal often attain considerable thickness, six to eight yards being not unusual. At Brühl, near Cologne, the brown-coal bed is in places as much as 340 feet thick. Most of the brown coal from this bed is compressed into briquettes for household use, the development of the industry having been greatly facilitated by the fact that the Rhine is available for transport. The proprietors of one of the mines in this district have had the enterprise to add to their equipment an electric central station, which by means of 50 miles of main cables, furnishes a large area with light and power. The brown coal, which is mined in open workings, is taken by electric haulage to seven boilers, the steam being used for engines that drive triphase generators yielding currents at 5,700 volts. Thick deposits of brown coal are found at various localities in the British colonies. At Lal Lal, in Victoria, for example, the beds are 150 feet thick, and are covered by basalt. At the Miranda Mine in New Zealand the seam is 55 feet thick.

Peat.-Peat or turf is the most recent product of the decay of plants under special conditions of air and moisture, either in swampy ground, actually under water, or in mountainous regions kept moist by fogs. It consists of the fossil remains of moss mixed with other plants. It may be classified (1) according to the localities where it has been formed as lowland and mountain peat; (2) according to its age, as recent peat with distinct vegetable structure, and old peat of a dark brown or black colour, with mere traces of organic texture; (3) according to the mode in which it has been extracted, as cut peat or dredge peat. Peat bogs are of frequent occurrence in all parts of the world. In Europe, the most considerable are in Russia, Ireland, Germany, Scandinavia, and Austria. In France, Italy, and Spain, peat is of less frequent occurrence. Air-dried peat is used for heating boilers, evaporating pans, pottery kilns, and for domestic purposes. Even when dried, peat cannot be economically substituted for coal on account of its bulky nature and consequent cost for carriage, its want of uniformity, and its large percentage of water and ash. Many well-directed efforts have been made of late years to utilise the material in the very extensive peat bogs of Ireland, Scandinavia, and elsewhere, by producing by compression or other treatment, a compact and useful fuel; and there can be no doubt that compressed peat will be more generally used when the cost of coal is much enhanced.

II. THE BITUMEN SERIES. Besides coal, there are a series of hydrocarbons occurring in various forms: as natural gas, liquid as petroleum, viscous as ozokerite, and solid as asphalt. There are too, gradations from one to another. Whilst coals appear to have been formed from the decomposition of plants, the bitumens are probably distillation products from organic matter of animal origin.

No

Natural Gas.-This subject has already been dealt with in papers by Prof. J. Dewar* and Mr. W. Topleyt. In the petroleum districts of Pennsylvania and adjoining States, natural gas issues from the strata at a depth of 500 to 2,000 feet below the surface, and when boreholes are sunk to the accumulation, the gas rises under a mean pressure of 150 to 200 lbs. per square inch. When first reached, the tension of the gas is very high, 1,000 lbs. per square inch being not unusual. Since 1821, natural gas has been utilised in a limited way; but since the reading of Mr. Andrew Carnegie's paper on natural gas before the Iron and Steel Institute in 1885, it has attained an extraordinarily rapid development for industrial purposes. For generating steam, 1,000 cubic feet of gas is equal to 80 to 133 lbs. of coal. The neighbourhood of Pittsburg, in Pennsylvania, is the most important locality for natural gas. record is kept of the production in the United States. The amount of coal, however, displaced by gas in 1901 was 8,458,600 tons. There were 10,297 wells producing, and there were 21,848 miles of natural gas mains, the gas being used in 1,545 industrial establishments. It has been found that the supply of gas in a reservoir is limited. Indeed, some have already been exhausted. On the other hand, a gas well in Ohio has been blowing for twenty years without any apparent diminution in the supply. Natural gas is also being produced on a commercial scale in England by the Natural Gas Fields of England, Limited (capital £100,000). It was discovered in west Sussex as long ago as 1836, and later discoveries induced the London, Brighton, and South Coast Railway Company to light Heathfield Station with natural gas. Bore holes were then sunk 300 to 400 feet through impervious sandstone and marl with successful results, and at Heathfield some 80 houses are now using natural gas for lighting and heating. It is burnt in the street lamps, and gas-engines are being driven by it. According to the Journal of the Society of Arts, vol. 33, p. 771. + Ibid, vol. 39, p. 421.

official statistics compiled for the Home Office by Sir C. Le Neve Foster the production of natural gas in 1902 was 150,000 cubic feet. Experimental borings are being made over 200 square miles of the county of Sussex, and if it can be proved that the Weald is underlain by a gasfield the industrial conditions of the south of England will be entirely changed.

Petroleum.-The subject of petroleum has already been exhaustively dealt with in a course of Cantor Lectures by Mr. Boverton Redwood, and has since been discussed in papers read before the Society by Mr. R. D. Oldham,† Mr. G. Stockfleth, and Sir Marcus Samuel. I need, therefore, deal but briefly with this industry which during the past 40 years has acquired such remarkable importance. It dates from the year 1859, when Colonel Edwin L. Drake bored at Titusville, Pennsylvania, the first oil well. The utilisation of the distillates of the crude oil, benzine and petroleum, and the heavy oils as residues, soon not only acquired important development in the United States, but furnished an important article of export. The still more important petroleum field of Baku, on the eastern side of the Caucasus on the Caspian Sea, where the occurrence of petroleum was described by Marco Polo in the 13th century, and where the existence of the eternal fires of the Apsheron peninsula has been known for 2,500 years, has been developed since 1870. The importance of the petroleum industry is best shown by the fact that some 20,000,000 tons are produced annually; of this the United States and Baku produce the bulk, Galicia, Roumania, Burma, the Dutch Indies. Japan, and Canada comparatively small quantities. The world's production of petroleum in 1901, was as follows:

The residues, known in Russia as Mazout, compete in the oilfields with coal. They serve for heating locomotives and steam ships. The transport of the oil is noteworthy. For retail trade it is loaded in the well-known blue barrels or in rectangular tinplate cases. For transport on a large scale, tank steamers are used, and tank waggons on the railways, the loading and unloading being effected by pumping in pipe lines. Certainly, Drake's enterprise in 1859 marked an epoch in the history of mining. Compare the carriage of oil in barrels on waggons and in flat boats down the creek to the river, with the pipe-line transportation from the wells to the coast. Compare, too, the £4 a barrel paid for Drake's crude oil with the 4s. a barrel at the end of the century.

Being cheap and developing great heat on combustion, petroleum is largely used as fuel. The average calorific power of the crude oil is 10,000 calories. Various varieties give the following calorific powers, in calories:-West Virginia, heavy oil, 10, 180; West Virginia, light oil, 10,223; Pennsylvania, light oil, 9,963; Ohio, heavy oil, 10,399; Java, 10,831; Roumania, 10,005; and Baku, 11,460. The recent development of the Texas oil fields has resulted in a great increase in the number of steamers, locomotives, and factories using oil fuel in the United States, whilst in South America, Peruvian oil has been largely used. The Borneo, Japan, and Sumatra oilfields are supplying large quantities for consumption in India, Japan, and Australia. No oil is so suitable for illumination as that of Pennsylvania. In many circumstances petroleum is a very economical fuel. It occupies less space than coal, a ton of coal occupying 40 cubic feet, oil 33 cubic feet. It also presents the advantages of greater efficiency of evaportion per unit measure of heating surface, more equable generation of steam, greater cleanliness and freedom from ash, avoidance of heat caused by frequent opening of furnace doors, and instantaneous extinction of furnace fires.

The Russian supplies are the most extensive, the chief district being to the north of Baku on the Caspian. At the present time some 2,000 boring derricks are in operation, and during 1902 they raised 11,000,000 tons of crude petroleum. The bore-holes have an average depth of 200 yards, some being as much as 500 yards. The derricks are 30 to 60 feet high. As motive power for boring and pumping from the wells, steam is usually employed. In 1898 a company was formed to erect a central electric station of 1,500 horse

power in order to use electro-motors instead of steam-engines. Each of the derricks is furnished with a motor which is used for boring and subsequently for winding up the oil. It sometimes happens that when oil is struck, the petroleum, after demolishing the derrick, spouts up as a fountain (Fig. 2). A difficulty in the way of installing alternating current motors, is the risk of fire, for, unfortunately, conflagrations are frequent and extensive. In the spring of 1902, for example, more than 100 derricks were burned. Disastrous fires, due to incendiarism, have

FIG. 2.

(capital £1,150,000); the European Petroleum Company, Ltd. (capital £1,100,000); and the Spies Petroleum Company, Ltd. (capital £700,000). British capital is also being invested in the Chatma oil field, a promising field almost midway between Batoum and Baku.

Although no petroleum is raised in Great Britain, oil shale is in Scotland the basis of a considerable industry. The county of Linlithgow yields more than half the production. The mineral occurs in beds in sandstone at the base of the carboniferous strata. Similar deposits are mined at Autun and Buxìères-laGrue in France, and in New South Wales. In 1901 the production of oil shale in Scotland

PETROLEUM FOUNTAIN AT BAKU.

also occurred quite recently. The electromotors are consequently placed on a solid masonry foundation, and in a separate brick building (Fig. 3.) The motor is thus kept away from the derrick, which is specially in danger of fire. The production of oil is largely in the hands of Nobel Brothers, and of the Rothschilds. Of late years, however, a large amount of British capital has been invested in these undertakings, the chief companies being the Russian Petroleum and Liquid Fuel Company, Ltd. (capital £1,200,000); the Baku Russian Petroleum Company, Ltd. (capital £1,500,000); the Schibaieff Petroleum Company, Ltd. *According to Mr. L. Gaster, experience in the Roumanian oilfields tends to show that the polyphase motor is the best for boring and pumping, and, if properly enclosed, can be brought quite near to the well without danger.

ELECTROMOTOR HOUSE AT BAKU OIL-Wells.

was 2,354,356 tons, and of kerosene shale in New South Wales 54,774 tons. The oil shale mines of Scotland yield a product of greater money value than the tin mines of Cornwall.

Ozokerite. In 1883 this mineral-wax formed the subject of a course of Cantor lectures by Mr. L. Field, who described the properties of the mineral and its use in the manufacture of candles. The most important deposit of ozokerite mined is at Boryslaw, in Galicia. As long ago as 1856 petroleum was obtained in this district from shallow wells. The mineralwax was known, but it was not until 1862 that it was raised and purified. It fills fissures in Miocene shale and sandstones forming a kind of network. Serious gas explosions are not uncommon. The output of ozokerite in Galicia in 1901 was 2,707 tons. Mining Journal of the Society of Arts, vol. 31, pp. 821, 833, 846, 857, 809, 881,

Brunswick veins of asphalt, known as albertite, occur in bituminous schists and are mined on a large scale. Very pure asphalt is also obtained from the Dead Sea. This material, which is not worked at present, was doubtless used in ancient times as water-tight cement in buildings. It was used by the ancient Egyptians for embalming their dead, and it is remarkable that there is no record of its use throughout the middle ages, up to the 18th century. A celebrated deposit that has been worked for a century, is the Pitch Lake of Trinidad. The lake is a mile and a-half inland from Brea. It is very irregular in shape, and about a mile in length. It is of unknown depth, and solid enough to be walked over. The pitch is hacked out by picks. Wherever it is abandoned for a few days, the cavity fills up from below. In one part of the lake the pitch is hot and plastic, and this soft spot is continually changing. Plant for dealing with the pitch on a large scale has been erected by the New Trinidad Lake Asphalt Company. Mr. J. W. Gordon and Professor Henry Louis

consider that at the present rate of extraction of about 120,000 tons per annum from the Pitch Lake, the deposit should still last for more than a century. In Barbados, manjak (mineral pitch) occurs in veins in infusorial earth.

The mining of asphalt rock has rapidly developed since the first asphalt pavement was laid down in Paris in 1838. The oldest mines are those of Seyssel, near Bellegarde on the Rhone, and of the Val de Travers in the Swiss Canton of Neuenberg. The asphalt rock of the Val de Travers is a bituminous limestone of cretaceous age. The bed is 12 to 24 feet in thickness, and contains 10 per cent. of bitumen. At the present time the mines of Ragusa, in the island of Sicily, are the most important, the production having increased from 4,000 tons in 1879, to 79,000 tons in 1901. The asphalt occurs in Miocene limestone, and contains 10 to 18 per cent. of bitumen. The product is very similar to those of Seyssel and Val de Travers, so that it can be mixed with them without lessening the binding properties. The output of the other mines in Europe (Seyssel, Val de Travers, Chieti in the Abruzzi, Limmer and Vorwohle in Hanover, Lobsann in Alsace, Auvergne, and Syzrane in Russia), may be estimated at 120,000 tons annually. In the United States asphalt is mined chiefly in Utah and California. The world's production is about 600,000 tons annually, the principal producing countries having raised in 1901 the following amounts:

Particulars of the production of Switzerland are not available. Small quantities are also produced in Russia, Mexico, Turkey in Asia, Colombia, Canada, and Holland. The average price of crude asphalt at Ragusa is 13s. per ton. Several English companies are engaged in asphalt mining. The Val de Travers Asphalt Paving Company, Ltd. (capital £100,000), registered in 1871, made in 1902 a trading profit of £42,256. The Limmer Asphalt Paving Company, Ltd. (capital £40,000), also registered in 1871, paid in 1901 a dividend of 10 per cent. and a bonus of 10 per cent. The Neuchâtel Asphalt Company, Ltd. (capital £569,880), paid in 1901 a dividend of 14s.

per £10 share. The United Limmer and Vorwohle Rock Asphalt Company, Ltd. (capital £60,000), paid for each of the 12 years up to 1901 a dividend of 10 per cent. and a bonus of 2 per cent.

Within the last few years asphalt deposits of considerable extent have been opened up in the Indian territory, United States. At Tar Springs the deposit occurs in a basin about a mile in diameter, the asphalt being met with in sand and sandstone which it has thoroughly impregnated. The overburden is removed and a thin capping of barren sandstone blasted off. The bed is then loosened by ploughs drawn by teams of four or six mules and excavated by wheeled scrapers. The sands contain 10 to 14 per cent. of asphalt, and three to six per cent. of heavy oil. The asphalt sands are tipped and shovelled to a feed bin, and conveyed thence to a disintegrator, which is heated by steam to facilitate the passage of the adhesive asphaltic material. The brokenup material is raised by an elevator to the concentrating apparatus in the upper part of the building. The concentration is based on the fact that the associated heavy oil adheres to the asphalt and buoys it up, while the sands, freed from both asphalt and oil, and washed by warm water, are discharged by an underconveyor. The asphalt and oil rise to the surface of the water, and are discharged by the upper conveyor. This method of separation was devised by Mr. R. V. La Grand, and is similar to the Elmore oil process of concentrating ores. The elimination of water and oil from the asphalt is effected by evaporation. The total loss in concentrating and refining, varies from four to six per cent. The refinery cost £8,000. The cost of mining is 4d. per cubic yard, and that of refining, about £2 per ton. The plant is designed for a capacity of 25 tons finished product per day of 24 hours.

Correspondence.

INDIA'S PLACE IN AN IMPERIAL
FEDERATION.

During the debate on Mr. J. M. Maclean's paper, it was noticeable that none of the speakers stated the factors to be dealt with in any readjustment of Indian Customs duties-the corpus on which the inquest was being held. Mr. Maclean did say that the figure of our whole trade with India (or, including that with Ceylon and the Straits, these two per

As to the forms and terms of this Table, two explanatory remarks may be needed: (a) the amounts are given in the recently adopted Dawkin's pounds (not true sterling, counted at fifteen rupees) as being more tangible for English readers, the several proportions serving as basis for comparison of each of the six factors; (b) Treasure is, of course, omitted on both sides, though that large factor would be essential in any estimate of India's full commercial balance sheet; but no one proposes to give preference to or penalise movements of specie in or out of India, more than by the present five per cent. imposed on imports of silver-other than those on State accounts for coinage purposes. So it will appear that the only factor to be dealt with in any scheme of differential duties is the 144 millions of foreign imports into British India, for it is not conceivable to tax exports from India. However, as a certain prominent authority has remarked, "Figures are only illustrations. . . the proof will be found in the argument :' and, as the arguments were fairly well surveyed by the experienced debaters on the 10th, these statistics, as above, will complete the subject matter.

W. MARTIN WOOD.

[Letters have been received from Sir Guilford Molesworth, Mr. M. E. J. Gheury, and Mr. H. H. Cunynghame, which will be printed in the next number.]

VOLUME LII. OF THE JOURNAL.-By an unfor. tunate oversight the numbers of the Journal 2662, Nov. 27; 2663, Dec. 4; 2664, Dec. 11; and 2665, Dec. 18, have had "Vol. LI." printed at the head of the first page of reading matter instead of Vol. LII." The correct number of the Volume is given on the cover of the Journals.