down as the muriate of silver, in the shape of a white curdy precipitate, which is insoluble in dilute acids, but is soluble in ammonia.

The sulphate of iron throws down the silver in a metallic state.

TELLURIUM.

Native Tellurium.-Colour-tin-white, with a shining metallic lustre in crystalline grains aggregated. Solitary or disseminated; foliated, easily fusible.

Found in veins in porphyry with iron pyrites, quartz, &c., alloyed with silver, lead, bismuth, &c.

Graphic Tellurium.—Colour-steel-grey, approaching tin-white, splendent or tarnished externally. Occurs-in small crystals generally so arranged as to present the appearance of writing; it is brittle, and yields easily to the knife. Contains-tellurium 60, gold 30, silver 10. Found as above with iron pyrites, quartz, calcareous spar, native gold, iron pyrites, &c.

Blow-pipe-dark grey metallic globule, brilliant and malleable.

Yellow Tellurium.-Is found silver-white, passing into yellow and grey of different shades. Occurs-in small crystals, bright metallic lustre. Consists of tellurium 44.75, gold 26.75, silver 8.5, lead 19.5.

Found in porphyry, with gold, native arsenic, sulphuret, manganese,

&c. &c.

Black Tellurium.-Colour-between dark lead-grey, and iron-black. Occurs-crystallized, yields easily to the knife, and is sectile, and in thin laminæ, is flexible.

Tellurium dissolves readily in nitric acid. Solution colourless. The oxide of tellurium best dissolves in aqua regia.

Carbonate of ammonia throws down an abundant white precipitate, soluble in excess of the precipitant. An excess of carbonate of potash strikes a green colour, which disappears on boiling the liquid, and does not again show itself.

TITANIUM.

This metal is very little known, it is something the colour of copper, but redder, very hard, and brilliant.

Anatase (Oxide of Titanium).-Occurs-in small crystals of the acute octohedron, by reflected light of various colours, as blue, clove-brown, reddish brown, or steel-grey. The structure is lamellar, fragments splendent and adamantine, varying from semi-transparent to opaque. By exposure to heat, the yellowish brown crystals turn deep blue.

Rutile (Oxide of Titanium).-Colour-reddish brown, in four or eightsided prisms, geniculated, often striated, sometimes in reticulated crystals. It occurs in the vein of the primitive rocks, with the ores of tin, with spathose, iron, &c., and often penetrates quartz, by slender hairs or thin wires. Red by transmitted light. In many places in England, Wales, and Scotland.

Found

Titan (Nigrin).-Colour-brownish black. In small loose angular masses; lamellar, lustre, shining or glimmering opaque, brittle. in primitive rocks, in debris of granite (Ceylon), fragments of granite with hyacinth, gold, rutile, oxidulated iron, &c. Said to contain 84

per cent. oxide of titanium. With borax, it melts into a hyacinth-red glass.

Titanium is very difficult to dissolve in acids; but, if first heated with caustic potash or soda, it is readily oxidized, and converted into titanic acid. When precipitated by alkali, from muriatic acid solution, washed, and then ignited, it forms lumps of light brown colour of great lustre. When titanic acid is heated to redness, it becomes lemon-yellow, which gets white on cooling.

In obtaining the acid solutions of titanic acid, do not use heat; muriatic acid is best.

The tincture of nutgalls throws down an orange-red precipitate : this is characteristic of titanium.

Menachanite.-Of a grey or iron-black colour. Occurs-in small angular grains. Structure-imperfect lamellar. The fracture fine-grained, even glistening lustre, between adamantine and metallic.

Found in St. Kevern, St. Stephen's, and other places in Cornwall. Contains 45 oxide of titanium, 51 oxide of iron. It has been found in Australia, New South Wales.

Iserine.-Of an iron or brownish black. Occurs-in grains or rounded pieces, of a deep black internally, the structure lamellar, cross fracture, conchoidal, with brilliant semi-metallic lustre, very hard. Stated at 48 oxide of titanium, and 48 oxide of iron. Has been found in Silesia, in Aberdeenshire, in Scotland, and Dr. Trail states, "it oozes out of a bed of cohering sand, on the shore of the Mersey, at Seacombe Ferry, opposite Liverpool."

Sphene.-Colour-greyish, yellowish, reddish, blackish brown, various shades of green, bluish, and greenish white. Amorphous, and when pounded is greyish white, also in crystals of various forms. It is found in primitive rocks, in various countries, and in Ireland, Scotland, Shetland, and Cornwall. Contains-35 oxide of titanium, 35 silex, 33 lime. On proper trial, it is likely that some valuable pigments may be obtained from the oxides of this metal.

TUNGSTEN.

Tungstate of Iron-Woolfran.-Found in the tinstone of the veins and beds of Saxony, Bohemia, and Cornwall. Colour-greyish and brownish blue. Massive and in crystals, right oblique-angled prisms. Fractureuneven; imperfect metallic, opaque. In elevated temperature, melted into globule, and the surface covered with small crystals of metallic lustre. Fuses with borax into green globule, melts with biphosphate of soda, into a deep red transparent bead.

Tungstate of Lead.-Very similar to the brown phosphate of lead. It is neither frequent nor plentiful.

Tungstate of Lime.—Colour-yellowish white, grey-white. Occursamorphous and crystallized.

Found in primitive rocks.

Tungstate of lime often resembles carbonate and sulphate of lead, and heavy spar. It is distinguished from the two first ores by not effervescing in acids; and from the last, by the yellow colour it assumes when

in nitre.

TIN.

Oxide.-Peroxide sometimes (rarely) occurs massive, fibrous, granular; generally crystallized.

Colour-all shades from light brown towards black, and sometimes in Cornwall the oxide of tin is met with in quite white, semi-transparent, and translucent sparkling glass-looking crystals; but very few, either of the miners or mine-captains, know much about the gangue, and matrices of the tin-veins. Tin is the only mineral which attracts the care or the attention of the miner. The tin-veins sometimes contain very considerable quantities of silver, and other valuable minerals, but all is wasted; nothing but the tin is attended to.

In

The oxide of tin belongs almost exclusively to the oldest of the primitive mountains, but not to the oldest granite. It is found in veins and beds, and often disseminated in certain descriptions of granite. Bohemia and Saxony, it is often in beds alternately with granite. It is stated by Klaproth to contain 77.5 tin, and 21.5 oxygen.

Tin Pyrites (Sulphuret of Tin).-It is massive. Colour-steel-grey, yellowish white, or yellow, and dead buff, and often all these shades are in blotches in the mass. Fracture-granular and uneven, passing into conchoidal, of a shiny lustre. It yields to the knife.

It has been worked in Wheal Rock, in Trewanance, in St. Agnes, and in Wheal Scorier, and is more frequent than is generally supposed. Constantine, Stenna Gwynn, St. Neot's, St. Stephen's, and other places. Commonly taken for "mundic." Contains 34 tin, 36 copper, 25 sulphur.

Blow-pipe. When finely pulverized, it is reducible on charcoal, by continued action, to the metallic state.

Various minerals have been taken as the oxide of tin, axinite, woolfran, &c. &c. The "clean tin" is not soluble in any acid, even if fused with carbonate of soda; but if five times its weight of caustic potash be mixed with it, and then ignited for a considerable time, near an hour, in crucible, the mass may then be dissolved in muriatic acid; then sulphureted hydrogen is passed through (the solution having been previously concentrated, and then diluted with water) as long as precipitate falls. The oxide of tin is then thrown down by caustic ammonia. The oxide of tin, in muriatic solution, may be precipitated in a metallic state by leaving a cylinder of zinc in it for some days. Collect, dry, cover with charcoal, and melt in crucible.

ZINC.

Native Zinc has not been found in a metallic state.

Sulphuret of Zinc (Blende, Black Jack).-Colour-brown, red, yellow, blackish brown, reddish black, also lead-colour. Occurs-massive, mamillated, fibrous, and crystallized. The structure is perfectly lamellar. It is transparent or opaque, and yields to the knife. Some of these blendes contain lead, silver, copper, gold, and arsenic.

Found in primitive and secondary rocks, and very commonly in the veins of lead, copper, and also with iron, tin, &c.

Contains-from 40 to 68 of zinc, and from 25 to 36 sulphur.

Red Oxide.-Colour-various shades of ruby-red, ruby or blood-red.

It occurs massive, investing, and micaceous, with shining lustre. ture-lamellar, translucent.

Contains-88 oxide of zinc.

Blow-pipe. All the above are infusible, without addition.

Struc

Silicious Oxide (Electro-Calamine).—Brown, greyish, bluish, yellowish white, also tinge of green, brownish, and blackish, externally, and irridescent. Massive, botryoidal, stalactitic, and crystallized. It is generally opaque, sometimes transparent. It yields to the knife, but is much harder than the carbonate of zinc. Oxide of zinc, 66.

Carbonate of Zinc.-Colour-mostly greyish, yellowish, or greenish brown. Occurs-compact, pseudomorphous, earthy, reniform, striated, cupriferous, and crystallized.

Contains-from 62 to 65 oxide of zinc.

Earthy Calamine.-White, greyish, or yellowish white. Dull and opaque. Occurs-massive, disseminated, and investing, and pseudomorphous. Commonly found in the shape of dog's-tooth spar, and generally externally dull and brownish. Calamine occurs in beds and veins in secondary limestone, commonly in lead veins and conglomerate rocks.Contains-from 64 to 71 oxide of zinc.

Sulphate.-Greyish, yellowish, reddish, and greenish white. Massive, stalactitic, botryoidal, investing. Structure-fibrous and radiated.

Shining, translucent. Soft and brittle.

It is generally found with blende, and some think it arises from its decomposition; but it sometimes occurs without blende, in Flintshire and in Cornwall.

Oxide of zinc, 27-Sulphuric acid, 22.

Liquid ammonia into the solution of zinc produces a white precipitate, which again dissolves by adding additional quantity of the test.

The sulphurets may be very finely powdered, and then digested in strong nitric acid until dissolved; then the oxide of zinc may be thrown down by carbonate of soda at boiling heat.

LIVES OF EMINENT ENGINEERS.

IT has been announced as part of the plan of the present work to give memoirs of eminent engineers, as illustrative of the progress of practical science. Perhaps we could choose none so appropriate as Watt, Trevithick, and Stephenson, and to whom the mining interest, as patrons of this work, are especially indebted. Watt, by the improvement of the low-pressure engine, gave vast resources to the miners of Cornwall and the coalbasins. Trevithick, by the invention of the high-pressure engine and the locomotive, gave no less impulse, and he enabled the steam-engine to be applied to the silver-mines of the mountainous regions of Peru. Stephenson, by inventing a safety-lamp, and by improving the locomotive engine, rendered two great services, while the latter has operated most powerfully in the development of the coal-fields and limestone quarries. Trevithick was a

pupil of the great mining school of Cornwall, Stephenson of that of Newcastle, each the head of his school.

As the life of Watt is well known-we have confined ourselves to a short sketch. For the lives of Trevithick and Stephenson we are indebted to Hyde Clarke, Esq.

LIFE OF JAMES WATT.

BY THE EDITOR.

JAMES WATT, the subject of cur notice, was born at Greenock, in Scotland, in the year 1736, where he was educated at the grammar-school, and at the age of sixteen apprenticed to a mathematical instrument maker, within two years after which he came to London, but subsequently returned to his native place. At the age of twenty-one we find him resident in the University of Glasgow, he having been appointed philosophical instrument maker to the College, where he remained for seven years, until the year 1764, when he established himself as an engineer, and was one of those consulted in the construction of the Caledonian Canal. It was about this period that his mind appears to have been more especially directed to the application and power of steam, arising from his having been engaged in repairing a model of a steam-engine constructed on the principles of Savery, by Newcomen and Cawley, a patent for which had been taken out at so distant a period as 1705. The model belonged to the class of natural philosophy in the College, and Watt tried various experiments for its efficient repair. After having devoted nearly four years to these and subsequent investigations, we find that in 1768 he completed his first engine, which differed from that of the model by the condensation of the steam taking place in a second vessel, so that the descent as well as ascent of the piston was produced by the force of the steam, and not by atmospheric pressure, as in the engine of Newcomen. It was not, however, until 1769 that he secured his first patent, having been materially assisted, in a pecuniary point of view, by Dr. Roebuck, in accomplishing his object, and effecting those several improvements to which be was prompted in the course of his experiments. It being found that the steam, in coming in contact with cold water, caused a loss of two-thirds of the fuel by condensation, Watt introduced a wooden pipe or tube instead of iron, considering the wood as a worse conductor of heat. This, however, had not the desired effect, as the wood was found to present less resistance to the sudden changes of temperature. With a view of counteracting the obstacles which thus presented themselves, he determined on passing the steam through an iron tube without cooling the walls or outer surface, and which may indeed be said to constitute the invention of the condenser. A small air-pump was also applied, which was worked by the piston, so as to get rid of the water in the condenser,-this being Watt's first great improvement. His second was that of enclosing the metal tubes in wood, so as to retain the heat, and admitting the steam above and below the piston, as it required to be depressed or raised, calculating with a degree of nicety the fuel necessary for producing a certain quantum or power of steam, and the volume or quantity of cold water required to condense it. At this time, however, it is to be regretted that Watt possessed not sufficient means for extending the utility of his discoveries. About seven years afterwards, Dr. Roebuck, who had become reduced in circumstances, disposed of his interest to Mr. Matthew Boulton, of Birmingham.

Watt having thus become associated with Boulton, active steps were taken for the construction of a steam-engine at their manufactory at Birmingham, which all connected with the mining interest were invited to visit, and which at the time excited much interest. Cornwall, which has made such great advances in