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In the United States, Georgia yields the bulk, the remainder being obtained from Alabama and Arkansas. The Arkansas bauxite occurs in the Fourche Mountain district and in Bryant township. At Bryant, it rests on kaolinised syenite, and has a thickness of about fifteen feet. Some of it is pisolitic, while the whole is of this character in the Fourche Mountain district. The deposits appear to have been due to the action of heated alkaline water the syenite, and to subsequent superficial chemical reactions on the deposits left by the springs.

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Other Earthy Minerals.-There are numerous other useful earthy minerals, some of Minerals which may be briefly mentioned. used as abrasives, oilstones and whetstones, grindstones and buhrstones, are in increasing demand from year to year. Some of these, crystalline quartz, garnet, corundum, and emery, will be incidently noticed under the head of precious stones. In the United States, the total value of all the natural abrasives produced in 1901 was £297,000. Infusorial earth, or kieselguhr, is largely used as a polishing powder as well as an absorbent for nitro-glycerine in the manufacture of dynamite. It is also used as ductor of heat for coating steam-pipe. It is a siliceous earth, consisting entirely of the microscopic shells of diatoms. It is found in the Lüneberg Moor in Hanover, in the Siegen district, in Scotland, and in Italy. In the United States, the most important deposit is at Red Mountain in Nevada. Pumice is also used for polishing. It is a glassy lava, rendered porous by the escape of gas through its mass when in the state of fusion. The most important source of supply is the Lipari Islands, which exported 6,834 tons in 1901. 'The deposit covers about 3,706 acres. Pelato, the centre of the industry, is an extinct crater, on which the accumulations of pumice reach in places a thickness of 650 feet. All material is now got from extremely primitive underground workings in a bed 3 to 12 feet thick. About 1,200 persons are engaged in the industry. In 1901 the production was 8,300 tons, valued at £31,000. In the mineral paint industry, there are several raw materials that may here be mentioned. The ochres, which consist chiefly of ferric hydrate, are largely used, while the clayey ferric oxide, bole, gives the well-known bright red colour. The world's production of ochre in 1901 included :

Monte

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The pumice sands and tuffs of the Eifel, known as trass, are used for making mortar, as is also puzzuolana, the volcanic ash that is quarried at the foot of Vesuvius. In the small group of useful minerals, not ores, occurring in mineral veins, barytes, fluorspar and strontianite are of considerable value.

In the United Kingdom, barytes or heavyspar is obtained from veins in Silurian rocks, or in the carboniferous limestone in three principal districts-Northumberland, Shropshire, and Ireland. The first supplies witherite, the carbonate; and the second and third, mainly heavy-spar, the sulphate. In the United States, this mineral is widely distributed. It is used chiefly for adulterating white lead. paint. The world's production in 1901, included, in metric tons-United States, 44,516; Germany, 88,000; United Kingdom, 28,054; Belgium, 22,800; Canada, 592. Fluorspar is mined in Derbyshire under the name of "Blue John." It is used as a flux in smelting operations, in the manufacture of hydrofluoric acid for etching glass, as a glaze for pottery, and in the manufacture of opalescent glass. By far the largest amount is used in fluxing iron. In 1901, the world's producduction comprised, in metric tons:- -United States, 17,768; Germany, 29,000:- United Kingdom, 4,232; France, 3,970. Sulphate of strontium is dug from shallow pits in Gloucestershire and Somersetshire. It is found in the red marl belonging to the Keuper beds. The chief supply is obtained from Hamm, in Westphalia, where seventeen mines, in 1901, produced 1,020 tons, valued at £73,875. There is small demand for the mineral. It is used by firework makers and in the treatment of beet sugar.

MEETINGS OF THE SOCIETY.
ORDINARY MEETINGS.

Wednesday Evenings, at 8 o'clock:-
JANUARY 20.-"Organ Design." By THOMAS
CASSON.

JANUARY 27.-"Ice Breakers and their Services." By ARTHUR GULSTON.

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LECTURE II.-FEBRUARY 1.-Methods of Refining - Bleaching — Demargarinating Processes-The Industry of Edible Oils and Fats-Butter Substitutes -Lard Substitutes-Chocolate Fats.

LECTURE III.-FEBRUARY 8.-Burning OilsPaint Oils-Lubricating Oils-Blown Oils-Boiled Oils-Varnish Industry-Linoleum Industry-Vulcanised Oils-Turkey red Oils-Modern Theory of Hydrolysis of Fats.

LECTURE IV.-FEBRUARY 15.-Mo lern Processes of Saponification-Candle Industry-Soap Industry - Manufacture of Glycerine-Recovery of Glycerine from Soap Lyes,

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Geographical, University of London, Burlington. gardens, W., 81 p.m.

Medical, 11, Chandos-street, W., 8 p.m.

Victoria Institute, 8, Adelphi-terrace, W.C., 41 p.m.
Rev. Arthur Elwin, “Ancestral Worship."
London Institution, Finsbury-circus, E.C., 5 p.m.
Mr. H. F. Gadow, "Mexico and its Natural
History."

TUESDAY, JAN. 12...Asiatic, 22, Albemarle-street, W., 5 p m.
Royal Institution, Albemarle-street, W., 5 p.m.
Prof. L. C. Miall," The Development and Trans-
formation of Animals." (Lecture I.)
Medical and Chirurgical, 20, Hanover-square, W.,
8 p.m.

Civil Engineers, 25, Great George-street, S.W..
8 p.m. Mr. Alexander Millar, "The Electrical
Re-Construction of the South London Tramways
on the Conduit System."

Anthropological, 3, Hanover-square, W., 8) p.m.
Colonial, Whitehall Rooms, Whitehall-place,
S.W., 8 p.m. Mr. C. C. Lance, "Australia as a
Food-Producing Country."

WEDNESDAY, JAN. 13...SOCIETY OF ARTS, John-street,
Adelphi, W.C., 5 p.m. (Juvenile Lecture.) Mr.
Eric Stuart Bruce, "The Navigation of the Air."
(Lecture II.)

Biblical Archæology, 37, Great Russell-street,
W.C., 41 p.m. Annual Meeting.

Japan Society, 20, Hanover-square, W., 8 p.m.
Mr. Chokuro Kadono, "The Bringing-up of
Japanese Girls."

Royal Literary Fund, 7, Adelphi-terrace, W.C., 3

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Antiquaries, Burlington-house, W., 8 p.m.
United Service Institution, Whitehall, S.W., 3 p.m.
Admiral Sir J. C. Dalrymple Hay, "The Necessity
of Training Boys for the Sea Service."
London Institution, Finsbury-circus, E.C., 6 p.m.
Dr. R. Hutchinson, "The Food of the People."
Royal Institution, Albemarle-street, W., 5 p.m.
Mr. G. R. M. Murray, "The Flora of the Ocean."
(Lecture I.)
Electrical Engineers, 25, Great George-street, S.W.,
8 p.m.
1. Discussion on Mr. P. V. McMahon's
paper, "The City and South London Railway:
working results of the Three-Wire System applied
to Traction, &c." 2. Dr. Hans Behn-Eschenburg
"The magnetic dispersion in Induction Motors,
and its influence on the design of these machines."
Historical, Clifford's Inn Hall, Fleet-street, E.C.,
5 p.m.

Mathematical, 22, Albemarle-street, W., 5 p.m.
FRIDAY, JAN. 15...Royal Institution, Albemarle-street, W.,
9 p.m., Lord Rayleigh, "Shadows."
Quekett Microscopical Club, 20, Hanover-square,
W.C., 8 p.m.

Mechanical Engineers, Storey's gate, Westminster,
S.W., 8 p.m. Sixth Report to the Alloys Research
Committee on "The Tempering of Steel," by the
late Sir William C. Roberts-Austen and Professor
William Gowland.

SATURDAY, JAN. 16... Royal Institution, Albemarle-street, W., 3 p.m. Mr. J. A. Fuller Maitland, "British Folk Song" (with vocal illustrations). (Lecture I.)

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The adjudicators under the will of the late Dr. Swiney are summoned to meet at the house of the Society of Arts, John-street, Adelphi, London, on Wednesday, January 20, 1904, at 4.30 p.m., to make the award in conformity with the terms of the bequest contained in the will of the testator.

(By Order)

HENRY TRUEMAN WOOD, Secretary.

COLOUR

EXHIBITION OF MECHANICAL
ENGRAVING AND
PRINTING.

The Board of Education, in co-operation with the Council of the Society of Arts, intend during the present year to hold, in the Victoria and Albert Museum, South Kensington, an Exhibition of Engravings produced by mechanical means, such as photogravure and other photographic processes, as a sequel to the Exhibition of Engraving and Etching held during last summer; and, as great advancements have been made in printing in colours since the Exhibition of Modern Illustration in 1901, specimens of colour printing will be

JUVENILE LECTURES.

On Wednesday afternoon, January 13th, Mr. ERIC STUART BRUCE, M.A, delivered the second and last lecture of his course of Juvenile Lectures of The Navigation of the Air," which dealt with Airships, Kites, and Flying Machines.

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Carlyle, in his History of the French Revolution," typifies balloons as beautiful but unguidable."

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Attempts have been made to navigate balloons in two ways. First, by mechanical propulsion; and, secondly, by utilising the air currents. A screw has been used to cut into the air, and as long as the power of the screw is greater than that of the wind the screwpropelled balloon can make progress even against the wind; but hitherto the power taken up on a balloon has only been sufficient to overcome very moderate winds. The action of a screw was shown, and Giffard's steam navigable balloon, Tissandier's electric balloon, and Krebs' and Renard's electric balloon were explained and illustrated by lantern views and maps of their journeys. Count Zeppelin's airship was shown floating in mid-air by the aerial graphoscope, an optical instrument which shows views in the air without a screen, and was explained by a number of views. Aluminium wire was broken up to show the brittleness of aluminium and how it was that this giant airship was wrecked in the end by the wind. These various navigable balloons or airships only made. return journeys against winds so light as to be practically calms. M. Santos Dumont is the

only man in the world who has made a return journey to a given spot up to time. This he did in 1891, when he gained the Deutsch prize of 100,000 francs; so that he has advanced aeronautics in practice though not in principle. His airships show originality in detail, and it is very much to his attention to detail that we inay ascribe his success. He introduced the ballonet or inner balloon, and a ballonet was shown within an outer balloon, empty and inflated, and its action in preserving rigidity in the outer balloon was shown by experiment, and the power of the rigid balloon to resist pressure was illustrated by dropping weights on it which rebounded. An airship sailed. round the room and made a return journey, and a vision of Santos Dumont's airship rounding the Eiffel Tower appeared in the air, followed by views of the incidents of his journeys. M. Santos Dumont has sailed against a wind of from four to five metres per second, which is a very slight breeze.

A vision of Severo's airship came next, followed by a series of experiments with hydrogen, burning soap bubbles, and red-hot platinum wire, and the electric spark in the centre of a globe of gas, showing that a safer place for motors would be in the centre of the gas of the balloon and not near the borderland just outside the balloon where hydrogen gas and air meet. The first British airship was that of Mr. Stanley Spencer which crossed London in 1902. The Lebaudy airship built throughout of steel, which was shown on the screen, has made 30 journeys, nearly all return ones; but it has hitherto only made way against very moderate winds.

In the first lecture it was stated that air currents flow in different directions. If we try to utilise them for airship travelling, we must improve the vertical up and down motion of our airships so as to save gas and ballast. Dr. Danilewsky tried to do this by his balloon, of which a picture was shown, and which may be described as between the lighter than air and the heavier than air principles, and Baron de Bradsky tried to get vertical motion in his airship by having a horizontal screw below it. The twisting action which caused the steel wires of Baron de Bradsky's balloon to break was shown by twisting a horizontal screw which twisted its supports.

Kites which rise to great heights and carry self-recording instruments are useful for this purpose, increasing our knowledge of air currents. American kites at Blue-hill Observatory have already flown over three miles

high. Pictures of scientific tailless kites followed. The box kite, the form most generally used, was explained, and a modification of it which has been taken out by the Scottish Antarctic Expedition was shown, also the various kites used in the first international kite competition at Findon, arranged by the Aeronautical Society in June last.

The consideration of kites leads up to that means by which it is hoped eventually to master the air, namely, the body heavier than air-the aeroplane. If the string of a kite is cut off and the kite supplied with a motor and screw propeller as adopted by Sir Hiram Maxim and Professor Langley, in their aeroplanes, we have the flying machine. Maxim's machine was shown on its rails. Langley's original unmanned aeroplane has actually flown successfully through the air for three quarters of a mile, though the new one has flown downwards into the water instead of upwards. The difficulty of such a flying machine is to balance it. In considering the body heavier than air, we are leaving behind the balloon which, though it is the "mule" of the air, yet holds us up. The motor-driven kite or flying machine is bound to be upset by the air currents if not automatically balanced, and a number of model flying machines were seen flying about the room, exhibiting by their erratic course how the air draughts affected them. The first to experiment with gliding machines for the purpose of practising balancing in the air was Lilienthal in 1891. A gliding machine, like a parachute, depends upon the resistance of the air. The first lecture began with a study of the resistance of the air, and ended with an example of its sustaining power, and now, at the end of the course, we are brought again face to face with this important fact. A gliding machine depends upon gravity for its motive power. Lilienthal was shown gliding through the air-he made some 2,000 glides, but was eventually killed, as was Pilcher, who was also shown gliding: Pilcher was killed in trying to glide from level ground. Pictures were also shown of the successful glides of the Messrs. Wright in America. At the forthcoming St. Louis Exhibition amongst the aeronautical prizes offered is one for gliding machines. In conclusion, simplicity in principle was urged as the basis of artificial flight; and a number of small "Penard" flying machines were given to the children.

The CHAIRMAN proposed a vote of thanks to Mr. Eric Bruce for his interesting course of lectures, which was carried unanimously.

LIST OF MEMBERS.

The new edition of the List of Members of the Society is now ready, and can be obtained by members on application to the Secretary.

COVERS FOR JOURNAL.

For the convenience of members wishing to bind their volumes of the Journal, cloth covers will be supplied, post free, for 1s. 6d. each, on application to the Secretary.

which they were thought to protect the wearer. Writing in 1644, Boetius de Boodt in his "Histoire des Pierreries," suggests that the substance of the gems, in consequence of their beauty, their lustre, and their dignity, is considered suitable for the dwelling and receptacle of good spirits; and thus when marvellous effects are produced by the precious stones, they should be attributed not to their inherent properties, but to the spirits. The jewellery of primitive people consisted of small stones with natural perforations. Later on, they learned to bore hard stones. As an example, I may mention the perforated chrysolite shown in a drawing in the "Hortus Sanitatis" of 1490.

Proceedings of the Society. In this work, it is asserted that chrysolite

CANTOR LECTURES.

THE MINING OF NON-METALLIC MINERALS.

BY BENNETT H. BROUGH. Lecture IV.-Delivered December 14th, 1903. Precious Stones.-Diamond-Corundum gemsEmerald-Other precious stones-Ornamental stones -Rare earths.

PRECIOUS STONES.

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The properties of precious stones already been dealt with in a course of Cantor Lectures by Professor H. A. Miers, and important papers on the subject have been contributed to the Society by Professor A. H. Church,† by Mr. A. Phillips, and by Mr. C. Giuliano. I need, therefore, in this lecture say but little regarding the mineralogy and the artistic interest of precious stones. Most of the precious stones have been known from the earliest periods of antiquity. Four magnificent bracelets of gold set with amethyst, turquoise, and lapis-lazuli, to which a date as remote as 5,000 B.C. is assigned, were found by Professor Flinders Petrie in his recent excavations at Abydos. The twelve stones on Aaron's breast-plate, engraved with the names of the twelve tribes, if it were possible to identify them with certainty, would still be regarded as precious. In early times, such stones were highly prized, not only as objects of ornament, but as charms possessing medicinal virtues; indeed the use of precious stones as jewellery appears to have arisen primarily from the magic powers attributed to them, by

• Journal of the Society of Arts, vol. 44, pp. 757, 769. + Ibid, vol. 29, p. 440.

Ibid, vol. 35. p. 438. \ [bid, vol. 37, p. 391.

drives away demons and the worst melancholy fears if pierced, and the hole filled up with ass's bristles, and the stone bound on the left arm. Even in pre-historic times precious stones were bored and worn In as beads. Mexico, for example, amazon-stone, chrysoprase, amethyst, red jasper, and brightlycoloured fluorspar were used. In Central Europe, amber was the earliest gem. Soft soapstone, which can be polished with the hand, was also worked into beads.

As a group, precious stones are chiefly distinguished from other minerals by their transparency, lustre, hardness, colour, specific gravity, electric properties, refractive power, and symmetrical crystal form. They are found disseminated through rocks, in veins, fissures or cavities, or in alluvial deposits derived from the disintegration of rocks. The esteem in which precious stones are held for use as personal jewellery does not decrease. Indeed, in the United States, the year 1902 showed the greatest importation on record of precious stones. According to statistics collected for the Government by Mr. G. F. Kunz, the production in the United States in 1902 was as follows:

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