tor of the natural history department of the British museum. He entered upon the discharge of his new duties with a zeal which never relaxed, and found time also to prepare papers for publication in the "Transactions" of the chief scientific societies in Europe and America. One of the first and most important of these was that on "Crustaceology" (1813), a branch of natural history to which he devoted much attention, and in which he made many important discoveries. Its leading feature was the separation of the myriopoda, arachnida, and insecta from the crustacea, all of which had been grouped by Linnæus under insecta. In this arrangement he showed his predilection for the natural system of classification, as opposed to the artificial system of Linnæus to which English naturalists were strongly attached; and his subsequent labors in this direction are considered to have produced the first movement toward the adoption of the system now in vogue in England. His other most important works were the "Zoological Miscellany," a serial commenced in 1814 after his appointment to the British museum, and completed in 1817 in 3 vols.; and the first part of the "History of the British Crustacea," of which 17 parts appeared. His severe labors finally so affected his eyesight and his general health that he was obliged to resign his curatorship, and to a great extent the pursuit of his favorite studies. In 1826 he visited southern Europe, and occupied himself at intervals in making collections of the insects in the localities where he happened to be residing. These are preserved in the Plymouth institution and by the Devon and Cornwall natural history society. He died of cholera. His love of animals was excessive, and he had a peculiar faculty for subduing the most ferocious kinds. One of the most faithful and attached companions of his walks was a wolf which he had tamed.

LEAD, a bluish gray soft metal, of specific gravity, when condensed by rolling, 11.44, otherwise 11.35; chemical symbol Pb, from Lat. plumbum; equivalent, 103.57. It is easily cut with a knife, and when rubbed on paper leaves a dark bluish gray streak. Its lustre when freshly cut is strongly metallic; but the bright surface soon tarnishes in consequence of the formation of a thin film of basic carbonate of the oxide of the metal. Lead is so ductile that it can be rolled into thin sheets, or drawn into wire; but its tenacity is feeble, a wire inch in diameter supporting only 30 lbs. It possess es flexibility in a high degree, but is deficient in elasticity. It has a perceptible peculiar odor, but no taste. It fuses at 612° F., and on cooling tends to assume octahedral crystalline forms. By repeated heating and cooling below its freezing point it is said to acquire a permanent increase of bulk. In a brasqued crucible in the high heat of a furnace, estimated at 130° Wedgwood, it volatilizes, losing of its weight in an hour. It even takes fire and burns with a bluish white light in the air at a very high temperature, forming with oxygen the oxide

known as litharge. When finely divided, the metal is even more inflammable than gunpowder, as shown by Faraday. When about melting, its surface is covered with an iridescent pellicle of oxide of lead, which soon gives place to the yellow litharge. Lead is scarcely attacked by hydrochloric acid, even concentrated and boiling; and sulphuric acid has no effect upon it unless the acid is in this condition, when it converts the metal into an insoluble sulphate. Nitric acid diluted and cold readily dissolves it. Lead forms alloys with all the metals except iron; and some of these combinations are much used in the arts. Type metal is formed of various proportions of lead and antimony, with sometimes a little tin; pewter, of lead and tin; 2 parts of lead and one of tin form the alloy used for organ pipes, and in this and other proportions it is the solder of the plumbers. Equal parts of lead and tin make the solder of the tin smiths, a very combustible alloy, which when heated to redness gives a combination of oxides of lead and tin known as polishing putty, and much used in the arts for polishing hard substances and preparing enamels. It is on the strong affinity of lead for gold and silver that the method of separating these metals from earthy admixtures and oxidizable metals is based, the lead seizing upon them when melted together, and then being made to separate from them when converted into an oxide by the process described in ASSAYING and CUPELLATION. The qualities of the metal render it ill adapted for purposes requiring strength; but being easily moulded from a fused state into any form, its cheapness and weight recommend it as the best material for small shot and musket balls, and its cast sheets when rolled thin serve as an excellent lining of cisterns, and are used for those in chemical works designed to contain sulphuric and hydrochloric acids. Lead pipe. is exceedingly convenient for conveying water, being transported in coils like ropes, and when unwound for laying furnished in any desired length; it is easily bent to turn corners, cut without difficulty, and joined with great facility by soldering. If ruptured by water freezing within the pipe, the damage is limited to a small space, and is easily repaired. These advantages cause lead pipe to be very generally used, notwithstanding the evil effects often experienced by the poisonous qualities of the salts produced by the chemical action of the water and of the foreign substances carried along with it. This subject will be specially considered in the course of this article.-Little is known of the early use of lead. The metal is several times named in the Old Testament, and it is supposed that the word translated tin should have been rendered lead. Mines were worked in Britain at a very early period, Camden stating that lead was obtained from Cornwall and Cumberland before the Christian era. Under the government of the Romans the metal must have been largely produced, judging from the Roman relics found about the old mines, among which are blocks

of lead with Latin inscriptions. The Saxons continued these operations, and one of their . mines near Castleton was dedicated to Odin. A sarcophagus of lead lined with linen has been found near Wirksworth, which must have been of as early date as the year 714. In Spain also lead together with silver and copper was obtained by the Romans from numerous mines on the southern slope of the Sierra Nevada; and in some of these mines recently reopened were found old Roman and Moorish lamps and other tools. Many other European countries are known to have produced lead as far back as the 10th to the 14th century; but out of Europe there are no records nor evidences preserved of ancient lead mining. Prescott states that the ancient Mexicans procured lead with silver and tin from the mines of Tarco, but no further mention is made of the metal. Even at the present day there seem to be no lead mines of importance known excepting in Europe and the United States; a fact which should argue neither a deficiency in the general distribution of the prevalent ore (the sulphuret or galena), nor difficulty in extracting from it the metal, which indeed is one of the easiest metallurgical processes; but the fact is probably due to the little use to which the metal can be applied by ignorant races. The Chinese, however, must work extensive lead mines from the amount of the metal which they consume as a lining for their tea chests.-Lead occurs in a great number of mineral combinations, but few of them will require notice as sources of supply of the metal. It has been found native at Alston Moor in Cumberland, disseminated with galena in a quartzose rock; also in a lead mine near Carthagena in Spain, and at another in Ireland. The sulphuret or galena furnishes nearly all the lead of commerce. This is a compound of one atom of lead and one of sulphur, consequently yielding when pure 86.55 of lead and 13.45 of sulphur in 100 parts. Its hardness is 2.5-2.75; specific gravity 7.25-7.7. It is not malleable, and is too brittle to be cut with a knife, but is easily crushed to a gray powder. The color of the mineral is a lead or blackish gray. Its crystals are cubic, or readily cleave into cubes. The ore also occurs in granular masses more or less mixed with quartz and other gangues, and with zinc blende and iron and copper pyrites. The freshly cleaved faces of the crystals have the lustre of metallic mirrors, and masses of the pure ore of perfect crystalline structure have been met with more than 5 feet in thickness and weighing several tons. Galena fuses easily, requiring little more heat than lead to melt it. It is more volatile than lead, and as it evaporates it is decomposed, and its vapors are converted into sulphate of lead. Melted in contact with charcoal, it is readily reduced to metal. Silver in the state of sulphuret probably occurs in all galena as a trace at least, but very commonly in quantities sufficient to furnish a few ounces, and from this to 100, and in rare cases 200 oz. of silver to the ton of lead. Such ores are known as argenti

ferous galena. In some of the mines of Freiberg galenas are found containing of silver, and are then properly considered silver ores. In Mexico many of the silver ores worked are of this class. At Tarnowitz in Prussian Silesia silver constitutes the weight of some of the galena. In the European mines the silver is an important object of exploration, and is profitably extracted when found only in the proportion of 3 oz. to the ton of lead; but the lead is not neglected, as it is in Mexico. In the United States argentiferous galenas are not treated for silver, except at the Washington mine in North Carolina, where silver is procured from other varieties of ore as well. Galena is sometimes found, as in Derbyshire, England, coating the walls of the veins in thin mirror-like sheets, which are called slickensides. These when accidentally scratched have the singular property of exploding with a loud report. Galena is the principal ore of nearly every lead mine. It is found in the crystalline rocks and metamorphic slates in veins associated with a great variety of other metals; and in the stratified rocks from the lower silurian to the lias in veins of various forms, and in beds, the last often being only the expansion of the materials of the veins between the planes of the strata. In Cumberland, England, where galena is extensively mined in the metalliferous or carboniferous limestone, which underlies the millstone grit, this mode of occurrence of the ores is distinguished by the name of flat veins or strata veins. These are productive usually but a short distance from the "rake" veins (or true veins cutting the strata) with which they connect. In this district, comprising a portion of Cumberland and adjacent parts of the counties of Durham and York, and furnishing more than half of all the lead product of Great Britain, the veins traverse the parallel and alternating beds of limestone and sandstone; in the former attaining their maximum thickness and yield of ore, and in the latter contracting and becoming poor. The features of this lead region are exhibited in that of Missouri, Iowa, and Wisconsin, where lead ores are extensively worked in the lower silurian limestones which also alternate with sandstones. A few mines in Cumberland have been profitably worked in sandstone, and in the United States the hard grit of the Shawangunk mountain in Ulster co., N. Y., has proved a repository of large quantities of galena found in veins cutting the strata.-Another ore which furnishes some lead to commerce is the carbonate, called also ceruse and white lead ore (PbO, CO2), a compound of oxide of lead 83.5 and carbonic acid 16.5 per cent., containing metallic lead 77.5 per cent. It occurs in acicular, tabular, and various crystalline forms derived from a right rhombic prism, of adamantine lustre, sometimes transparent, and exhibiting the phenomenon of double refraction. The mineral is brittle with conchoidal fracture; hardness 3-3.5; specific gravity 6.465-6.48, the earthy varieties sometimes 5.4. When of this structure, the mineral

is frequently colored by the presence of other metals, green, blue, or brown, and black. It is associated with galena in most localities of the latter, but is not often found as a workable ore. At the Missouri lead mines it was formerly rejected in large quantities through ignorance of its true character; but since this has been understood it has added many millions of pounds of lead to the production of these mines. It was especially abundant at Mine La Motte, Mo. In St. Lawrence co., N. Y., it has been largely obtained for smelting in an impure pulverulent form, and was known as lead ashes. It contained sulphate of lead and carbonate of lime, and was evidently produced by the reaction of the last named compound upon galena. The Washington mine, Davidson co., N. C., the Perkiomen and other mines near Phoenixville, Penn., and the Mine La Motte, Mo., and others in the United States, have furnished splendid crystallizations of this ore, as well as considerable quantities for the furnace.-Phosphate of lead, or pyromorphite, has commonly been regarded as a rare mineral; but at the mines near Phoenixville it has been largely worked, the furnaces sometimes being chiefly supplied with this beautiful green crystallized ore, which in the upper levels of some of the mines furnished of the whole metallic product. It occurs in hexagonal prisms, sometimes transparent, but generally green from sesquioxide of chromium, yellow, or brown and orange yellow from intermixture with chromate

of lead. It is of resinous lustre and brittle texture; hardness, 3.5-4; specific gravity, 6.597.05. The ore is a mixture in variable proportions of phosphate of lead, chloride of lead, phosphate of lime, and fluoride of calcium, the last often replacing some chloride of lead, and arsenic acid some of the phosphoric acid. The proportion of phosphate of lead is usually from 77 to 89 per cent., and of chloride of lead from 9.5 to 10.8 per cent. The ore is fused without difficulty, and the button obtained on charcoal with the blowpipe presents angular faces on cooling.-The arseniate, sulphate, chloride, chromate, molybdate, and some other combinations of lead occur as beautiful minerals, associated especially in the Phoenixville mines with the other compounds named, but they are not of sufficient importance to be treated as productive ores.-The artificial compounds of lead, the oxides and carbonate, will be described after completing the account of the sources of supply and metallurgic treatment of the ores.-Great Britain has probably supplied more than half the lead product of Europe. In 1810 the annual yield of her mines was estimated by Villefosse at 12,500 tons; but Mr. Taylor considered this largely underrated, and in 1822 estimated the annual product at 31,900 tons, and in 1835 at 46,112 tons, of which Northumberland, Durham, and Cumberland furnished 19,626 tons. The following table exhibits the production in tons of the several lead districts for the years named:

50,211 55,705

that the most argentiferous galenas are found in the districts of crystalline and metamorphic rocks.

Spain follows Great Britain as the next largest lead-producing country in the world. An extraordinary impulse was given to the development of her mines after 1825. It is stated that in 1826 more than 3,000 mines had been opened in the sierras of Gador and Lujar, and the increased production of lead was so great, that many mines in England and Germany were ruined. In 1823 the production was 25,000 tons, and in 1827 it had increased to 42,000 tons, causing a great decline in the price of the metal. In 1845 there were 826 mines of argentiferous galena in operation, employing 8,000 miners and 38 smelting works in the Sierra de Almagrera. The production of these mines in that year was 108,230 lbs. troy of silver, and 8,350 tons of lead. The ore was found in metamorphic micaceous slates, containing intercalated beds of trap and porphyry, and was disseminated in bunches lying in the lines of the stratification. These were most productive in

silver near the surface, the galena often yielding from 130 to 180 oz. to the ton. The ancient mines between Carthagena and Almeria have within a few years again been worked, and much lead has been extracted from the immense piles of old Roman slags, and from the inferior qualities of carbonate of lead rendered refractory by its intermixture with blende and pyrites. Some of the most important mines were worked in the granite hills of Linares upon the southern slope of the Sierra Morena, and these have produced enormous masses of galena. Catalonia, Granada, and Murcia have productive mines, and also the district above the town of Canjayar. For 1847 and 1849 the production of Spain was rated at about 30,000 tons each year. The metal is largely exported to the United States, France, and the countries up the Mediterranean. In Prussia about 7,195 tons of lead are reported to have been produced in 1851, together with 26,493 lbs. troy of silver, derived from argentiferous lead and copper ore. The mines are chiefly in Silesia and the Rhine provinces. The Hartz mountains are supposed to produce from 5,000 to 6,000 tons of lead and 30,000 to 35,000 lbs. of silver annually. The principal mines are near Clausthal in the Upper Hartz, where the veins are found most productive when split up and ramifying through the paleozoic strata in narrow threads, constituting what the Germans call a Stockwerk. Such a repository of ore, known as Rosenhöfer Zug, a little west of Clausthal, spreads out through 300 feet in width. In the Andreasberg group of veins is that known as the Samson vein, on which is the deepest mine now worked in the world. Rich collections of ore found at a depth of about 2,100 feet led to the workings being continued to the depth of 2,520 feet. (See HARTZ,) The skilful and economical methods applied to the treatment of the ores of this district render it profitable to keep mines in operation that would be abandoned in most other countries. The annual product of Saxony is said to be nearly 2,000 tons. Lead and silver are extracted in comparatively unimportant quantities in nearly all other European countries, but the product of none beside those named is estimated to amount to more than 1,000 tons of lead, except those of Austrian Illyria. For 10 years preceding 1847 her average annual product is put down at 3,253 tons, and the whole annual product of the Austrian empire during these years at only 3,837 tons, of which Hungary furnished 246 tons. The duchy of Nassau, having an area of only 82 German square miles, contains several hundred mines in operation, and among them about 30 of argentiferous lead, some of which have been worked since the year 1158. They are in argillaceous slates and sandstones of the silurian period. The annual product was a few years since stated to be about 600 tons of lead and 2,500 lbs. of silver.-In the United States, lead mines have been worked in the metamorphic rocks of the New England states, northern and eastern New York, Pennsylvania, and North

Carolina, and the chief ore, galena, is of frequent occurrence along the metamorphic belt of the Appalachian chain. But with the exception of the mine (also producing silver) in Davidson co., N. C., all these enterprises have proved unprofitable, and the mines have been abandoned, though some of them, as those of St. Lawrence co., N. Y., and possibly Shelburne, N. H., would have justified continued operations. The Coal Hill mine near Rossie, St. Lawrence co., in 3 years preceding 1839, is known to have produced about 1,800 tons of lead. It has been worked only to the depth of about 180 feet, principally by an open cut of the extreme length of 440 feet. The vein is nearly vertical in gneiss rock, and averages about 2 feet in width. The veinstone is calcareous spar, through which the galena and occasionally the earthy carbonate of lead is disseminated. Vugs or cavities frequently occur lined with splendid crystals of galena, and others of double refractive calcareous spar. One of the latter, nearly transparent, in Yale college cabinet, weighs 165 lbs. The galena contains but a mere trace of silver; it is also remarkably free from hurtful associations of other metals, as blende and iron and copper pyrites. Other similar veins are found in the same vicinity; and the time must come when they will be extensively worked. Detailed accounts of this and the other lead mines of the United States, most of which can be little more than named in this article, may be found in "The Metallic Wealth of the United States," by J. D. Whitney. At Southampton, Mass., lead mining was commenced in 1765 in an immense and very conspicuous true vein at the contact of the red sandstone of the Connecticut river valley and coarse-grained feldspathic granite. The lode consists of quartz containing sulphate of baryta, galena, some blende, and copper pyrites. Neither this nor the similar veins in Northampton and Easthampton have paid for the expenditures which at various times have been incurred in their exploration. At Middletown, Conn., the existence of lead ore was probably known in 1651, when a license was granted to Gov. John Winthrop to work mines of this and other specified mineral productions, with particular reference to any he might discover near Middletown. There is no tradition of the time when the mine was first worked. In 1852 it was reopened and worked to some extent. The ore is highly argentiferous galena, but not abundant. Shipments made to England yielded 25 to 75 oz. of silver to 21 cwt. of lead; and what was remarkable, a peculiar fine-grained variety of the ore, such as is usually found to be most argentiferous, proved to be only as rich in silver as the coarsely cubical ore. The vein consists chiefly of quartz, often in crystallized plates or combs, with some cale spar, sulphate of baryta, and fluor spar, also blende and iron and copper pyrites. It is from 10 inches to 3 feet in thickness, and is included in silicious and micaceous slates, with the dip and direction of which it

appears at the surface to coincide. In Dutchess co., N. Y., explorations were made for lead in 1740, and during the revolutionary war the committee of public safety sought to obtain supplies there. Veins of argentiferous galena are found also in Columbia, Washington, and Rensselaer cos., but have never proved productive. They traverse the strata near the junction of the metamorphic slates and limestones. The principal one is the Ancram or Livingston mine in Columbia co. On the other side of the Hudson river lead mines have been worked at various localities in the unaltered silurian limestones and sandstones; but these, too, have all been abandoned as unprofitable. The most productive among them were in the Shawangunk grit of Ulster co., which overlies the Hudson river slate group. On the W. slope of the Shawangunk mountain, at Ellenville, several nearly vertical veins have been followed into the hard sandstone, the strata of which and the direction of the mountain ridge they cross nearly at right angles. The principal one of these yielded in 1853 galena which produced about 459,000 lbs. of lead, and 60 to 70 tons of pyritous copper, 50 tons of which produced 24.3 per cent. of metal. The vein was unlike the true veins of the metamorphic rocks, having no gangue or veinstones, but wherever productive filled between the walls with rich galena and pyritous copper, the former sometimes being 5 feet thick unmixed with other matters. In places it contracted to a knife-edge seam in the hard sandstone, and again opened out in hollow fissures, one of which, extending to more than 100 feet in depth, with an equal horizontal range, has never been completely explored. It was partially filled with tough yellow clay, in which were imbedded loose fragments of sandstone, magnificent bunches of quartz crystals, and lumps of lead and copper ores; and its walls were also lined in places with the same ores. In these features a striking resemblance is exhibited to the so called "openings" of frequent occurrence in the western lead mines, although found there only in limestone. The vein is moreover like those of the western mines in lacking veinstones,. and probably also in being limited to certain rock formations, beneath which it will not prove productive. But as the lead-bearing rock is there limestone, and as limestone overlies the Shawangunk grit, it will be interesting to trace the vein into the calcareous rock, which, concealed beneath the soil of the valley, cannot be far off. It is true that the lead-bearing rock of the West is somewhat lower in position than the Shawangunk grit; and the Niagara limestone that overlies this grit is not productive in lead at the West, although largely developed in the vicinity of the lead mines; hence nothing can be predicted as to the characters which the vein will assume in entering the limestone. Before reaching the western states the grit rock, like most of the other sandstones, thins out. Though the lead veins lack the character of

"true veins," they prove more productive for the amount of ground worked than those thus designated. This is the case with the Ulster mine, while the extent of the formation stretching up the side of the mountain for 1,500 feet, and below to unknown depths, with a thickness on the course of the vein probably exceeding 500 feet, insured abundant working ground for extensive mining operations. The extreme hardness of the rock caused the mining to be expensive; but though abandoned in 1854 as unprofitable, this is no doubt one of the lead mines of the Atlantic states the working of which will again be prosecuted.-In Chester and Montgomery cos., Penn., near Phoenixville, is a group of lead and copper mines, in a small district of only 5 or 6 miles in length by 2 or 3 in breadth, some of the remarkable productions of which have already been noticed. They occur in gneiss and the red shale and sandstone of the middle secondary, cutting the strata in direction and dip. Nearly all the veins, of which there are 12 or more, are parallel to each other, directed N. 32°-35° E. and dipping steeply S. E. When confined chiefly to the gneiss, they produce as a general rule lead ores; when included in the red shale, their principal product is copper ores. Quartz and iron pyrites make up the larger part of the lodes, the latter in the upper portions of the mine decomposed to a soft brown gossan. This material sometimes yields 10 oz. of silver to the ton. Prof. H. D. Rogers, from whose "Geology of Pennsylvania" these data are obtained, enumerates the following large variety of metallic constituents of the Wheatley lode, beside the gangue of quartz and sulphate of baryta: of lead-sulphate, carbonate, phosphate, arseniate, molybdate, chromate, chromomolybdate, arsenio-phosphate, sulphuret, and antimonial argentiferous; of zinc-sulphuret, carbonate, and silicate; of copper-native metal, sulphuret, black oxide, malachites green and blue; of iron-the oxide containing silver, pyrites, brown spar, and hematite; native silver; black oxide of manganese. Native sulphur is also met with. This mine was opened in 1851, and up to Sept. 1854, had produced, according to the manager's report, 1,800 tons of lead ore, principally phosphate, estimated to yield 60 per cent. lead. The Chester county mining company commenced operations in 1850 in the same vicinity, and up to Nov. 1851, had smelted 190,400 lbs. of dressed ore, almost exclusively phosphate, which produced about 47 per cent. lead. Dr. Genth found this kind of ore to contain 1.6 oz. of silver in 2,000 lbs.; the coarsely granular galena gave 16.2 oz., and the radiated and finely granular galena 11.9 oz. Operations ceased at these and the other adjacent mines in 1854 and 1855.-In S. W. Virginia and E. Tennessee many lead mines, not in the metamorphic belt, but in the great silurian limestone formation of the valley of Virginia, have been worked with greater or less success for many years past, their ores being compact and crystallized carbonate of lead as well as galena. Those belonging to