FOOTNOTE:

[1] The English Bible does not use Lat. _Dives_ (rich) as a proper

name, saying merely "a certain rich man." The idea that Dives was a

proper name arose from the Vulgate _quidam dives_, whence it became a

conventional name for a rich man.

LAZARUS, EMMA (1849-1887), American Jewish poetess, was born in New

York. When the Civil War broke out she was soon inspired to lyric

expression. Her first book (1867) included poems and translations which

she wrote between the ages of fourteen and seventeen. As yet her models

were classic and romantic. At the age of twenty-one she published

_Admetus and other Poems_ (1871). _Admetus_ is inscribed to Emerson, who

greatly influenced her, and with whom she maintained a regular

correspondence for several years. She led a retired life, and had a

modest conception of her own powers. Much of her next work appeared in

_Lippincott's Magazine_, but in 1874 she published a prose romance

(_Alide_) based on Goethe's autobiography, and received a generous

letter of admiration from Turgeniev. Two years later she visited Concord

and made the acquaintance of the Emerson circle, and while there read

the proof-sheets of her tragedy _The Spagnoletto_. In 1881 she published

her excellent translations of Heine's poems. Meanwhile events were

occurring which appealed to her Jewish sympathies and gave a new turn to

her feeling. The Russian massacres of 1880-1881 were a trumpet-call to

her. So far her Judaism had been latent. She belonged to the oldest

Jewish congregation of New York, but she had not for some years taken a

personal part in the observances of the synagogue. But from this time

she took up the cause of her race, and "her verse rang out as it had

never rung before, a clarion note, calling a people to heroic action and

unity; to the consciousness and fulfilment of a grand destiny." Her

poems, "The Crowing of the Red Cock" and "The Banner of the Jew" (1882)

stirred the Jewish consciousness and helped to produce the new Zionism

(q.v.). She now wrote another drama, the _Dance to Death_, the scene of

which is laid in Nordhausen in the 14th century; it is based on the

accusation brought against the Jews of poisoning the wells and thus

causing the Black Death. The _Dance to Death_ was included (with some

translations of medieval Hebrew poems) in _Songs of a Semite_ (1882),

which she dedicated to George Eliot. In 1885 she visited Europe. She

devoted much of the short remainder of her life to the cause of Jewish

nationalism. In 1887 appeared _By the waters of Babylon_, which consists

of a series of "prose poems," full of prophetic fire. She died in New

York on the 19th of November 1887. A sonnet by Emma Lazarus is engraved

on a memorial tablet on the colossal Bartholdi statue of Liberty, New

York.

See article in the _Century Magazine_, New Series, xiv. 875 (portrait

p. 803), afterwards prefixed as a _Memoir_ to the collected edition of

_The poems of Emma Lazarus_ (2 vols., 1889). (I. A.)

LAZARUS, HENRY (1815-1895), British clarinettist, was born in London on

the 1st of January 1815, and was a pupil of Blizard, bandmaster of the

Royal Military Asylum, Chelsea, and subsequently of Charles Godfrey,

senior, bandmaster of the Coldstream Guards. He made his first

appearance as a soloist at a concert of Mme Dulcken's, in April 1838,

and in that year he was appointed as second clarinet to the Sacred

Harmonic Society. From Willman's death in 1840 Lazarus was principal

clarinet at the opera, and all the chief festivals and orchestral

concerts. His beautiful tone, excellent phrasing and accurate execution

were greatly admired. He was professor of the clarinet at the Royal

Academy of Music from 1854 until within a short time of his death, and

was appointed to teach his instrument at the Military School of Music,

Kneller Hall, in 1858. His last public appearance was at a concert for

his benefit in St James's Hall, in June 1892, and he died on the 6th of

March 1895.

LAZARUS, MORITZ (1824-1903), German philosopher, was born on the 15th of

September 1824 at Filehne, Posen. The son of a rabbinical scholar, he

was educated in Hebrew literature and history, and subsequently in law

and philosophy at the university of Berlin. From 1860 to 1866 he was

professor in the university of Berne, and subsequently returned to

Berlin as professor of philosophy in the kriegsakademie (1868) and later

in the university of Berlin (1873). On the occasion of his seventieth

birthday he was honoured with the title of _Geheimrath_. The fundamental

principle of his philosophy was that truth must be sought not in

metaphysical or a priori abstractions but in psychological

investigation, and further that this investigation cannot confine itself

successfully to the individual consciousness, but must be devoted

primarily to society as a whole. The psychologist must study mankind

from the historical or comparative standpoint, analysing the elements

which constitute the fabric of society, with its customs, its

conventions and the main tendencies of its evolution. This

_Völkerpsychologie_ (folk- or comparative psychology) is one of the

chief developments of the Herbartian theory of philosophy; it is a

protest not only against the so-called scientific standpoint of natural

philosophers, but also against the individualism of the positivists. In

support of his theory he founded, in combination with H. Steinthal, the

_Zeitschrift für Völkerpsychologie und Sprachwissenschaft_ (1859). His

own contributions to this periodical were numerous and important. His

chief work was _Das Leben der Seele_ (Berlin, 1855-1857; 3rd edition,

1883). Other philosophical works were:--_Ueber den Ursprung der Sitten_

(1860 and 1867), _Ueber die Ideen in der Geschichte_ (1865 and 1872);

_Zur Lehre von den Sinnestäuschungen_ (1867); _Ideale Fragen_ (1875 and

1885), _Erziehung und Geschichte_ (1881); _Unser Standpunkt_ (1881);

_Ueber die Reize des Spiels_ (1883). Apart from the great interest of

his philosophical work, Lazarus was pre-eminent among the Jews of the

so-called Semitic domination in Germany. Like Heine, Auerbach and

Steinthal, he rose superior to the narrower ideals of the German Jews,

and took a leading place in German literature and thought. He protested

against the violent anti-Semitism of the time, and, in spite of the

moderate tone of his publications, drew upon himself unqualified

censure. He wrote in this connexion a number of articles collected in

1887 under the title _Treu und Frei. Reden und Vorträge über Juden und

Judenthum_. In 1869 and 1871 he was president of the first and second

Jewish Synods at Leipzig and Augsburg.

See R. Flint, _The Philosophy of History in Europe_; M. Brasch,

_Gesammelte Essays und Characterköpfe zur neuen Philos. und

Literatur_; E. Berliner, _Lazarus und die öffentliche Meinung_; M.

Brasch, "Der Begründer de Völkerpsychologie," in _Nord et Sud_,

(September 1894).

LAZARUS, ST, ORDER OF, a religious and military order founded in

Jerusalem about the middle of the 12th century. Its primary object was

the tending of the sick, especially lepers, of whom Lazarus (see LAZAR)

was regarded as the patron. From the 13th century, the order made its

way into various countries of Europe--Sicily, Lower Italy and Germany

(Thuringia); but its chief centre of activity was France, where Louis

IX. (1253) gave the members the lands of Boigny near Orleans and a

building at the gates of Paris, which they turned into a lazar-house for

the use of the lepers of the city. A papal confirmation was obtained

from Alexander IV. in 1255. The knights were one hundred in number, and

possessed the right of marrying and receiving pensions charged on

ecclesiastical benefices. An eight-pointed cross was the insignia of

both the French and Italian orders. The gradual disappearance of

leprosy combined with other causes to secularize the order more and

more. In Savoy in 1572 it was merged by Gregory XIII. (at the instance

of Emanuel Philibert, duke of Savoy) in the order of St Maurice (see

KNIGHTHOOD AND CHIVALRY: _Orders of Knighthood, Italy_). The chief task

of this branch was the defence of the Catholic faith, especially against

the Protestantism of Geneva. It continued to exist till the second half

of the 19th century. In 1608 it was in France united by Henry IV. with

the order of Notre-Dame du Mont-Carmel. It was treated with especial

favour by Louis XIV., and the most brilliant period of its existence was

from 1673 to 1691, under the marquis de Louvois. From that time it began

to decay. It was abolished at the Revolution, reintroduced during the

Restoration, and formally abolished by a state decree of 1830.

See L. Mainbourg, _Hist. des croisades_ (1682; Eng. trans. by Nalson,

1686); P. Hélyot, _Hist. des ordres monastiques_ (1714), pp. 257, 386;

J. G. Uhlhorn, _Die christliche Liebesthätigkeit im Mittelalter_

(Stuttgart, 1884); articles in Herzog-Hauck's _Realencyklopädie für

protestantische Theologie_, xi. (1902) and Wetzer and Welte's

(Catholic) _Kirchenlexikon_, vii. (1891).

LEA, HENRY CHARLES (1825-1909), American historian, was born at

Philadelphia on the 19th of September 1825. His father was a publisher,

whom in 1843 he joined in business, and he retained his connexion with

the firm till 1880. Weak health, however, caused him from early days to

devote himself to research, mainly on church history in the later middle

ages, and his literary reputation rests on the important books he

produced on this subject. These are: _Superstition and Force_

(Philadelphia, 1866, new ed. 1892); _Historical Sketch of Sacerdotal

Celibacy_ (Philadelphia, 1867); _History of the Inquisition of the

Middle Ages_ (New York, 1888); _Chapters from the religious history of

Spain connected with the Inquisition_ (Philadelphia, 1890); _History of

auricular Confession and Indulgences in the Latin Church_ (3 vols.,

London, 1896); _The Moriscos of Spain_ (Philadelphia, 1901), and

_History of the Inquisition of Spain_ (4 vols., New York and London,

1906-1907). He also edited a _Formulary of the Papal Penitentiary in the

13th century_ (Philadelphia, 1892), and in 1908 was published his

_Inquisition in the Spanish Dependencies_. As an authority on the

Inquisition he stood in the highest rank of modern historians, and

distinctions were conferred on him by the universities of Harvard,

Princeton, Pennsylvania, Giessen and Moscow. He died at Philadelphia on

the 24th of October 1909.

LEAD (pronounced _leed_), a city of Lawrence county, South Dakota,

U.S.A., situated in the Black Hills, at an altitude of about 5300 ft., 3

m. S.W. of Deadwood. Pop. (1890) 2581, (1900) 6210, of whom 2145 were

foreign-born, (1905) 8217, (1910) 8392. In 1905 it was second in

population among the cities of the state. It is served by the Chicago,

Burlington & Quincy, the Chicago & North-Western, and the Chicago,

Milwaukee & St Paul railways. Lead has a hospital, the Hearst Free

Library and the Hearst Free Kindergarten, and is the see of a Roman

Catholic bishopric. It is the centre of the mining interests of the

Black Hills, and the Homestake Gold Mine here contains perhaps the

largest and most easily worked mass of low-grade ore and one of the

largest mining plants (1000 stamps) in the world; it has also three

cyanide mills. From 1878 to 1906 the value of the gold taken from this

mine amounted to about $58,000,000, and the net value of the product of

1906 alone was approximately $5,313,516. For two months in the spring of

1907 the mine was rendered idle by a fire (March 25), which was so

severe that it was necessary to flood the entire mine. Mining tools and

gold jewelry are manufactured. The first settlement was made here by

mining prospectors in July 1876. Lead was chartered as a city in 1890

and became a city of the first class in 1904.

LEAD, a metallic chemical element; its symbol is Pb (from the Lat.

_plumbum_), and atomic weight 207.10 (O = 16). This metal was known to

the ancients, and is mentioned in the Old Testament. The Romans used it

largely, as it is still used, for the making of water pipes, and

soldered these with an alloy of lead and tin. Pliny treats of these two

metals as _plumbum nigrum_ and _plumbum album_ respectively, which seems

to show that at his time they were looked upon as being only two

varieties of the same species. In regard to the ancients' knowledge of

lead compounds, we may state that the substance described by Dioscorides

as [Greek: molybdaina] was undoubtedly litharge, that Pliny uses the

word minium in its present sense of red lead, and that white lead was

well known to Geber in the 8th century. The alchemists designated it by

the sign of Saturn [symbol].

_Occurrence._--Metallic lead occurs in nature but very rarely and then

only in minute amount. The chief lead ores are galena and cerussite; of

minor importance are anglesite, pyromorphite and mimetesite (qq.v.).

Galena (q.v.), the principal lead ore, has a world-wide distribution,

and is always contaminated with silver sulphide, the proportion of noble

metal varying from about 0.01 or less to 0.3%, and in rare cases coming

up to ½ or 1%. Fine-grained galena is usually richer in silver than the

coarse-grained. Galena occurs in veins in the Cambrian clay-slate,

accompanied by copper and iron pyrites, zinc-blende, quartz, calc-spar,

iron-spar, &c.; also in beds or nests within sandstones and rudimentary

limestones, and in a great many other geological formations. It is

pretty widely diffused throughout the earth's crust. The principal

English lead mines are in Derbyshire; but there are also mines at

Allandale and other parts of western Northumberland, at Alston Moor and

other parts of Cumberland, in the western parts of Durham, in Swaledale

and Arkendale and other parts of Yorkshire, in Salop, in Cornwall, in

the Mendip Hills in Somersetshire, and in the Isle of Man. The Welsh

mines are chiefly in Flint, Cardigan and Montgomery shires; the Scottish

in Dumfries, Lanark and Argyll; and the Irish in Wicklow, Waterford and

Down. Of continental mines we may mention those in Saxony and in the

Harz, Germany; those of Carinthia, Austria; and especially those of the

southern provinces of Spain. It is widely distributed in the United

States, and occurs in Mexico and Brazil; it is found in Tunisia and

Algeria, in the Altai Mountains and India, and in New South Wales,

Queensland, and in Tasmania.

The native carbonate or cerussite (q.v.) occasionally occurs in the pure

form, but more frequently in a state of intimate intermixture with clay

("lead earth," _Bleierde_), limestone, iron oxides, &c. (as in the ores

of Nevada and Colorado), and some times also with coal ("black lead

ore"). All native carbonate of lead seems to be derived from what was

originally galena, which is always present in it as an admixture. This

ore, metallurgically, was not reckoned of much value, until immense

quantities of it were discovered in Nevada and in Colorado (U.S.). The

Nevada mines are mostly grouped around the city of Eureka, where the ore

occurs in "pockets" disseminated at random through limestone. The crude

ore contains about 30% lead and 0.2 to 0.3% silver. The Colorado lead

district is in the Rocky Mountains, a few miles from the source of the

Arkansas river. It forms gigantic deposits of almost constant thickness,

embedded between a floor of limestone and a roof of porphyry. Stephens's

discovery of the ore in 1877 was the making of the city of Leadville,

which, in 1878, within a year of its foundation, had over 10,000

inhabitants. The Leadville ore contains from 24 to 42% lead and 0.1 to

2% silver. In Nevada and Colorado the ore is worked chiefly for the sake

of the silver. Deposits are also worked at Broken Hill, New South Wales.

Anglesite, or lead sulphate, PbSO4, is poor in silver, and is only

exceptionally mined by itself; it occurs in quantity in France, Spain,

Sardinia and Australia. Of other lead minerals we may mention the basic

sulphate lanarkite, PbO·PbSO4; leadhillite, PbSO4·3PbCO3; the basic

chlorides matlockite, PbO·PbCl2, and mendipite, PbCl2·2PbO; the

chloro-phosphate pyromorphite, PbCl2·3Pb3(PO4)2, the chloro-arsenate

mimetesite, PbCl2·3Pb3(AsO4)2; the molybdate wulfenite, PbMoO4; the

chromate crocoite or crocoisite, PbCrO4; the tungstate stolzite, PbWO4.

_Production._--At the beginning of the 19th century the bulk of the

world's supply of lead was obtained from England and Spain, the former

contributing about 17,000 tons and the latter 10,000 tons annually.

Germany, Austria, Hungary, France, Russia and the United States began

to rank as producers during the second and third decades; Belgium

entered in about 1840; Italy in the 'sixties; Mexico, Canada, Japan

and Greece in the 'eighties; while Australia assumed importance in

1888 with a production of about 18,000 tons, although it had

contributed small and varying amounts for many preceding decades. In

1850 England headed the list of producers with about 66,000 tons; this

amount had declined in 1872 to 61,000 tons. Since this date, it has,

on the whole, diminished, although large outputs occurred in isolated

years, for instance, a production of 40,000 tons in 1893 was followed

by 60,000 tons in 1896 and 40,000 in 1897. The output in 1900 was

35,000 tons, and in 1905, 25,000 tons. Spain ranked second in 1850

with about 47,000 tons; this was increased in 1863, 1876 and in 1888

to 84,000, 127,000 and 187,000 tons respectively; but the maximum

outputs mentioned were preceded and succeeded by periods of

depression. In 1900 the production was 176,000 tons, and in 1905,

179,000 tons. The United States, which ranked third with a production

of 20,000 tons in 1850, maintained this annual yield, until 1870, when

it began to increase; the United States now ranks as the chief

producer; in 1900 the output was 253,000 tons, and in 1905, 319,744

tons. Germany has likewise made headway; an output of 12,000 tons in

1850 being increased to 120,000 tons in 1900 and to 152,590 in 1905.

This country now ranks third, having passed England in 1873. Mexico

increased its production from 18,000 tons in 1883 to 83,000 tons in

1900 and about 88,000 tons in 1905. The Australian production of

18,000 tons in 1888 was increased to 58,000 tons in 1891, a value

maintained until 1893, when a depression set in, only 21,000 tons

being produced in 1897; prosperity then returned, and in 1898 the

yield was 68,000 tons, and in 1905, 120,000 tons. Canada became

important in 1895 with a production of 10,000 tons; this increased to

28,654 tons in 1900; and in 1905 the yield was 25,391 tons. Italy has

been a fairly steady producer; the output in 1896 was 20,000 tons, and

in 1905, 25,000 tons.

_Metallurgy._

The extraction of the metal from pure (or nearly pure) galena is the

simplest of all metallurgical operations. The ore is roasted (i.e.

heated in the presence of atmospheric oxygen) until all the sulphur is

burned away and the lead left. This simple statement, however, correctly

formulates only the final result. The first effect of the roasting is

the elimination of sulphur as sulphur-dioxide, with formation of oxide

and sulphate of lead. In practice this oxidation process is continued

until the whole of the oxygen is as nearly as possible equal in weight

to the sulphur present as sulphide or as sulphate, i.e. in the ratio S :

O2. The heat is then raised in (relative) absence of air, when the two

elements named unite into sulphur-dioxide, while a regulus of molten

lead remains. Lead ores are smelted in the reverberatory furnace, the

ore-hearth, and the blast-furnace. The use of the first two is

restricted, as they are suited only for galena ores or mixtures of

galena and carbonate, which contain not less than 58% lead and not more

than 4% silica; further, ores to be treated in the ore-hearth should run

low in or be free from silver, as the loss in the fumes is excessive. In

the blast-furnace all lead ores are successfully smelted. Blast-furnace

treatment has therefore become more general than any other.

Three types of reverberatory practice are in vogue--the English,

Carinthian and Silesian. In Wales and the south of England the process

is conducted in a reverberatory furnace, the sole of which is paved

with slags from previous operations, and has a depression in the

middle where the metal formed collects to be let off by a tap-hole.

The dressed ore is introduced through a "hopper" at the top, and

exposed to a moderate oxidizing flame until a certain proportion of

ore is oxidized, openings at the side enabling the workmen to stir up

the ore so as to constantly renew the surface exposed to the air. At

this stage as a rule some rich slags of a former operation are added

and a quantity of quicklime is incorporated, the chief object of which

is to diminish the fluidity of the mass in the next stage, which

consists in this, that, with closed air-holes, the heat is raised so

as to cause the oxide and sulphate on the one hand and the sulphide on

the other to reduce each other to metal. The lead produced runs into

the hollow and is tapped off. The roasting process is then resumed, to

be followed by another reduction, and so on.

A similar process is used in Carinthia; only the furnaces are smaller

and of a somewhat different form. They are long and narrow; the sole

is plane, but slopes from the fire-bridge towards the flue, so that

the metal runs to the latter end to collect in pots placed _outside_

the furnace. In Carinthia the oxidizing process from the first is

pushed on so far that metallic lead begins to show, and the oxygen

introduced predominates over the sulphur left. The mass is then

stirred to liberate the lead, which is removed as _Rührblei_. Charcoal

is now added, and the heat urged on to obtain _Pressblei_, an inferior

metal formed partly by the action of the charcoal on the oxide of

lead. The fuel used is fir-wood.

The Silesian furnace has an oblong hearth sloping from the fire-bridge

to the flue-bridge. This causes the lead to collect at the coolest

part of the hearth, whence it is tapped, &c., as in the English

furnace. While by the English and Carinthian processes as much lead as

possible is extracted in the furnace, with the Silesian method a very

low temperature is used, thus taking out about one-half of the lead

and leaving very rich slags (50% lead) to be smelted in the

blast-furnace, the ultimate result being a very much higher yield than

by either of the other processes. The loss in lead by the combined

reverberatory and blast-furnace treatment is only 3.2%.

In Cumberland, Northumberland, Durham and latterly the United States,

the reverberatory furnace is used only for roasting the ore, and the

oxidized ore is then reduced by fusion in a low, square blast-furnace

(a "Scottish hearth furnace") lined with cast iron, as is also the

inclined sole-plate which is made to project beyond the furnace, the

outside portion (the "work-stone") being provided with grooves guiding

any molten metal that may be placed on the "stone" into a cast iron

pot; the "tuyère" for the introduction of the wind was, in the earlier

types, about half way down the furnace.

As a preliminary to the melting process, the "browse" left in the

preceding operation (half-fused and imperfectly reduced ore) is

introduced with some peat and coal, and heated with the help of the

blast. It is then raked out on the work-stone and divided into a very

poor "grey" slag which is put aside, and a richer portion, which goes

back into the furnace. Some of the roasted ore is strewed upon it,

and, after a quarter of an hour's working, the whole is taken out on

the work-stone, where the lead produced runs off. The "browse," after

removal of the "grey" slag, is reintroduced, ore added, and, after a

quarter of an hour's heating, the mass again placed on the work-stone,

&c.

In the more recent form of the hearth process the blocks of cast iron

forming the sides and back of the Scottish furnace are now generally

replaced in the United States by water-cooled shells (water-jackets)

of cast iron. In this way continuous working has been rendered

possible, whereas formerly operations had to be stopped every twelve

or fifteen hours to allow the over-heated blocks and furnace to cool

down. A later improvement (which somewhat changes the mode of working)

is that by Moffett. While he also prevents interruption of the

operation by means of water-jackets, he uses hot-blast, and produces,

besides metallic lead, large volumes of lead fumes which are drawn off

by fans through long cooling tubes, and then forced through suspended

bags which filter off the dust, called "blue powder." Thus, a mixture

of lead sulphate (45%) and oxide (44%) with some sulphide (8%), zinc

and carbonaceous matter, is agglomerated by a heap-roast and then

smelted in a slag-eye furnace with grey slag from the ore-hearth. The

furnace has, in addition to the usual tuyères near the bottom, a

second set near the throat in order to effect a complete oxidation of

all combustible matter. Much fume is thus produced. This is drawn off,

cooled and filtered, and forms a white paint of good body, consisting

of about 65% lead sulphate, 26% lead oxide, 6% zinc oxide and 3% other

substances. Thus in the Moffett method it is immaterial whether metal

or fume is produced, as in either case it is saved and the price is

about the same.

In smelting at once in the same blast-furnace ores of different

character, the old use of separate processes of precipitation,

roasting and reduction, and general reduction prevailing in the Harz

Mountains, Freiberg and other places, to suit local conditions, has

been abandoned. Ores are smelted raw if the fall of matte (metallic

sulphide) does not exceed 5%; otherwise they are subjected to a

preliminary oxidizing roast to expel the sulphur, unless they run too

high in silver, say 100 oz. to the ton, when they are smelted raw. The

leading reverberatory furnace for roasting lead-bearing sulphide ores

has a level hearth 14-16 ft. wide and 60-80 ft. long. It puts through

9-12 tons of ore in twenty-four hours, reducing the percentage of

sulphur to 2-4%, and requires four to six men and about 2 tons of

coal. In many instances it has been replaced by mechanical furnaces,

which are now common in roasting sulphide copper ores (see SULPHURIC

ACID). A modern blast-furnace is oblong in horizontal section and

about 24 ft. high from furnace floor to feed floor. The shaft, resting

upon arches supported by four cast iron columns about 9 ft. high, is

usually of brick, red brick on the outside, fire-brick on the inside;

sometimes it is made of wrought iron water-jackets. The smelting zone

always has a bosh and a contracted tuyère section. It is enclosed by

water-jackets, which are usually cast iron, sometimes mild steel. The

hearth always has an Arents siphon tap. This is an inclined channel

running through the side-wall, beginning near the bottom of the

crucible and ending at the top of the hearth, where it is enlarged

into a basin. The crucible and the channel form the two limbs of an

inverted siphon. While the furnace is running the crucible and channel

remain filled with lead; all the lead reduced to the metallic state in

smelting collects in the crucible, and rising in the channel,

overflows into the basin, whence it is removed. The slag and matte

formed float upon the lead in the crucible and are tapped, usually

together, at intervals into slag-pots, where the heavy matter settles

on the bottom and the light slag on the top. When cold they are

readily separated by a blow from a hammer. The following table gives

the dimensions of some well-known American lead-furnaces.

_Lead Blast-Furnace._

+----------------------+------+----------+--------------+

| Locality. | Year.| Tuyère |Height, Tuyère|

| | | Section. | to Throat. |

+----------------------+------+----------+--------------+

| | | In. | Ft. |

| Leadville, Colorado | 1880 | 33 × 84 | 14 |

| Denver, " | 1880 | 36 × 100 | 17 |

| Durango, " | 1882 | 36 × 96 | 12.6 |

| Denver, " | 1892 | 42 × 100 | 16 |

| Leadville, " | 1892 | 42 × 120 | 18 |

| Salt Lake City, Utah | 1895 | 45 × 140 | 20 |

+----------------------+------+----------+--------------+

A furnace, 42 by 120 in. at the tuyères, with a working height of

17-20 ft., will put through in twenty-four hours, with twelve men, 12%

coke and 2 lb. blast-pressure, 85-100 tons average charge, i.e. one

that is a medium coarse, contains 12-15% lead, not over 5% zinc, and

makes under 5% matte. In making up a charge, the ores and fluxes,

whose chemical compositions have been determined, are mixed so as to

form out of the components not to be reduced to the metallic or

sulphide state, typical slags (silicates of ferrous and calcium

oxides, incidentally of aluminium oxide, which have been found to do

successful work). Such slags contain SiO2 = 30-33%, Fe(Mn)O = 27-50%,

Ca(Mg, Ba)O = 12-28%, and retain less than 1% lead and 1 oz. silver to

the ton. The leading products of the blast-furnace are argentiferous

lead (base bullion), matte, slag and flue-dust (fine particles of

charge and volatilized metal carried out of the furnace by the

ascending gas current). The base bullion (assaying 300 ± oz. per ton)

is desilverized (see below); the matte (Pb = 8-12%, Cu = 3-4%, Ag =

(1/3)-(1/5) of the assay-value of the base bullion, rest Fe and S) is

roasted and resmelted, when part of the argentiferous lead is

recovered as base bullion, while the rest remains with the copper,

which becomes concentrated in a copper-matte (60% copper) to be worked

up by separate processes. The slag is a waste product, and the

flue-dust, collected by special devices in dust-chambers, is

briquetted by machinery, with lime as a bond, and then resmelted with

the ore-charge. The yield in lead is over 90%, in silver over 97% and

in gold 100%. The cost of smelting a ton of ore in Colorado in a

single furnace, 42 by 120 in. at the tuyères, is about $3.

Refining.

The lead produced in the reverberatory furnace and the ore-hearth is

of a higher grade than that produced in the blast-furnace, as the ores

treated are purer and richer, and the reducing action is less

powerful. The following analysis of blast-furnace lead of Freiberg,

Saxony, is from an exceptionally impure lead: Pb = 95.088, Ag = 0.470,

Bi = 0.019, Cu = 0.225, As = 1.826, Sb = 0.958, Sn = 1.354, Fe =

0.007, Zn = 0.002, S = 0.051. Of the impurities, most of the copper,

nickel and copper, considerable arsenic, some antimony and small

amounts of silver are removed by liquation. The lead is melted down

slowly, when the impurities separate in the form of a scum (dross),

which is easily removed. The purification by liquation is assisted by

poling the lead when it is below redness. A stick of green wood is

forced into it, and the vapours and gases set free expose new surfaces

to the air, which at this temperature has only a mildly oxidizing

effect. The pole, the use of which is awkward, has been replaced by

dry stream, which has a similar effect. To remove tin, arsenic and

antimony, the lead has to be brought up to a bright-red heat, when the

air has a strongly oxidizing effect. Tin is removed mainly as a

powdery mixture of stannate of lead and lead oxide, arsenic and

antimony as a slagged mixture of arsenate and antimonate of lead and

lead oxide. They are readily withdrawn from the surface of the lead,

and are worked up into antimony (arsenic)--tin-lead and antimony-lead

alloys. Liquation, if not followed by poling, is carried on as a rule

in a reverberatory furnace with an oblong, slightly trough-shaped

inclined hearth; if the lead is to be poled it is usually melted down

in a cast-iron kettle. If the lead is to be liquated and then brought

to a bright-red heat, both operations are carried on in the same

reverberatory furnace. This has an oblong, dish-shaped hearth of acid

or basic fire-brick built into a wrought-iron pan, which rests on

transverse rails supported by longitudinal walls. The lead is melted

down at a low temperature and drossed. The temperature is then raised,

and the scum which forms on the surface is withdrawn until pure

litharge forms, which only takes place after all the tin, arsenic and

antimony have been eliminated.

Desilverizing.

Silver is extracted from lead by means of the process of cupellation.

Formerly all argentiferous lead had to be cupelled, and the resulting

litharge then reduced to metallic lead. In 1833 Pattinson invented his

process by means of which practically all the silver is concentrated

in 13% of the original lead to be cupelled, while the rest becomes

market lead. In 1842 Karsten discovered that lead could be

desilverized by means of zinc. His invention, however, only took

practical form in 1850-1852 through the researches of Parkes, who

showed how the zinc-silver-lead alloy formed could be worked and the

desilverized lead freed from the zinc it had taken up. In the Parkes

process only 5% of the original lead need be cupelled. Thus, while

cupellation still furnishes the only means for the final separation of

lead and silver, it has become an auxiliary process to the two methods

of concentration given. Of these the Pattinson process has become

subordinate to the Parkes process, as it is more expensive and leaves

more silver and impurities in the market lead. It holds its own,

however, when base bullion contains bismuth in appreciable amounts, as

in the Pattinson process bismuth follows the lead to be cupelled,

while in the Parkes process it remains with the desilverized lead

which goes to market, and lead of commerce should contain little

bismuth. At Freiberg, Saxony, the two processes have been combined.

The base bullion is imperfectly Pattinsonized, giving lead rich in

silver and bismuth, which is cupelled, and lead low in silver, and

especially so in bismuth, which is further desilverized by the Parkes

process.

The effect of the two processes on the purity of the market lead is

clearly shown by the two following analyses by Hampe, which represent

lead from Lautenthal in the Harz Mountains, where the Parkes process

replaced that of Pattinson, the ores and smelting process remaining

practically the same:--

+----------+-----------+----------+----------+------+----------+----------+----------+----------+----------+

| Process. | Pb. | Cu. | Sb. | As. | Bi. | Ag. | Fe. | Zn. | Ni. |

+----------+-----------+----------+----------+------+----------+----------+----------+----------+----------+

| Pattinson| 99.966200 | 0.015000 | 1.010000 | none | 0.000600 | 0.002200 | 0.004000 | 0.001000 | 1.001000 |

| Parkes | 99.983139 | 0.001413 | 0.005698 | none | 0.005487 | 0.000460 | 0.002289 | 0.000834 | 0.000680 |

+----------+-----------+----------+----------+------+----------+----------+----------+----------+----------+

Cupelling.

The reverberatory furnace commonly used for cupelling goes by the name

of the English cupelling furnace. It is oblong, and has a fixed roof

and a movable iron hearth (test). Formerly the test was lined with

bone-ash; at present the hearth material is a mixture of crushed

limestone and clay (3:1) or Portland cement, either alone or mixed

with crushed fire-brick; in a few instances the lining has been made

of burnt magnesite. In the beginning of the operation enough

argentiferous lead is charged to fill the cavity of the test. After it

has been melted down and brought to a red heat, the blast, admitted at

the back, oxidizes the lead and drives the litharge formed towards the

front, where it is run off. At the same time small bars of

argentiferous lead, inserted at the back, are slowly pushed forward,

so that in melting down they may replace the oxidized lead. Thus the

level of the lead is kept approximately constant, and the silver

becomes concentrated in the lead. In large works the silver-lead alloy

is removed when it contains 60-80% silver, and the cupellation of the

rich bullion from several concentration furnaces is finished in a

second furnace. At the same time the silver is brought to the required

degree of fineness, usually by the use of nitre. In small works the

cupellation is finished in one furnace, and the resulting low-grade

silver fined in a plumbago crucible, either by overheating in the

presence of air, or by the addition of silver sulphate to the melted

silver, when air or sulphur trioxide and oxygen oxidize the

impurities. The lead charged contains about 1.5% lead if it comes from

a Pattinson plant, from 5-10% if from a Parkes plant. In a test 7 ft.

by 4 ft. 10 in. and 4 in. deep, about 6 tons of lead are cupelled in

twenty-four hours. A furnace is served by three men, working in

eight-hour shifts, and requires about 2 tons of coal, which

corresponds to about 110 gallons reduced oil, air being used as

atomizer. The loss in lead is about 5%. The latest cupelling furnaces

have the general form of a reverberatory copper-smelting furnace. The

working door through which the litharge is run off lies under the flue

which carries off the products of combustion and the lead fumes, the

lead is charged and the blast is admitted near the fire-bridge.

Pattinson process.

In the _Pattinson_ process the argentiferous lead is melted down in

the central cast iron kettle of a series 8-15, placed one next to the

other, each having a capacity of 9-15 tons and a separate fire-place.

The crystals of impoverished lead which fall to the bottom, upon

coaling the charge, are taken out with a skimmer and discharged into

the neighbouring kettle (say to the right) until about two-thirds of

the original charge has been removed; then the liquid enriched lead is

ladled into the kettle on the opposite side. To the kettle, two-thirds

full of crystals of lead, is now added lead of the same tenor in

silver, the whole is liquefied, and the cooling, crystallizing,

skimming and ladling are repeated. The same is done with the kettle

one-third filled with liquid lead, and so on until the first kettle

contains market lead, the last cupelling lead. The intervening kettles

contain leads with silver contents ranging from above market to below

cupelling lead. The original Pattinson process has been in many cases

replaced by the Luce-Rozan process (1870), which does away with

arduous labour and attains a more satisfactory crystallization. The

plant consists of two tilting oval metal pans (capacity 7 tons), one

cylindrical crystallizing pot (capacity 22 tons), with two discharging

spouts and one steam inlet opening, two lead moulds (capacity 3½

tons), and a steam crane. Pans and pot are heated from separate

fire-places. Supposing the pot to be filled with melted lead to be

treated, the fire is withdrawn beneath and steam introduced. This

cools and stirs the lead when crystals begin to form. As soon as

two-thirds of the lead has separated in the form of crystals, the

steam is shut off and the liquid lead drained off through the two

spouts into the moulds. The fire underneath the pot is again started,

the crystals are liquefied, and one of the two pans, filled with

melted lead, is tilted by means of the crane and its contents poured

into the pot. In the meantime the lead in the moulds, which has

solidified, is removed with the crane and stacked to one side, until

its turn comes to be raised and charged into one of the pans. The

crystallization proper lasts one hour, the working of a charge four

hours, six charges being run in twenty-four hours.

Parkes process.

It is absolutely necessary for the success of the _Parkes_ process

that the zinc and lead should contain only a small amount of impurity.

The spelter used must therefore be of a good grade, and the lead is

usually first refined in a reverberatory furnace (the softening

furnace). The capacity of the furnace must be 10% greater than that of

the kettle into which the softened lead is tapped, as the dross and

skimmings formed amount to about 10% of the weight of the lead

charged. The kettle is spherical, and is suspended over a fire-place

by a broad rim resting on a wall; it is usually of cast iron. Most

kettles at present hold 30 tons of lead; some, however, have double

that capacity. When zinc is placed on the lead (heated to above the

melting-point of zinc), liquefied and brought into intimate contact

with the lead by stirring, gold, copper, silver and lead will combine

with the zinc in the order given. By beginning with a small amount of

zinc, all the gold and copper and some silver and lead will be alloyed

with the zinc to a so-called gold--or copper--crust, and the residual

lead saturated with zinc. By removing from the surface of the lead

this first crust and working it up separately (liquating, retorting

and cupelling), doré silver is obtained. By the second addition of

zinc most of the silver will be collected in a saturated

zinc-silver-lead crust, which, when worked up, gives fine silver. A

third addition becomes necessary to remove the rest of the silver,

when the lead will assay only 0.1 oz. silver per ton. As this complete

desilverization is only possible by the use of an excess of zinc, the

unsaturated zinc-silver-lead alloy is put aside to form part of the

second zincking of the next following charge. In skimming the crust

from the surface of the lead some unalloyed lead is also drawn off,

and has to be separated by an additional operation (liquation), as,

running lower in silver than the crust, it would otherwise reduce its

silver content and increase the amount of lead to be cupelled. A

zincking takes 5-6 hours; 1.5-2.5% zinc is required for desilverizing.

The liquated zinc-silver-lead crust contains 5-10% silver, 30-40% zinc

and 65-50% lead. Before it can be cupelled it has to be freed from

most of the zinc, which is accomplished by distilling in a retort made

of a mixture similar to that of the plumbago crucible. The retort is

pear-shaped, and holds 1000-1500 lb of charge, consisting of liquated

crust mixed with 1-3% of charcoal. The condenser commonly used is an

old retort. The distillation of 1000 lb. charge lasts 5-6 hours,

requires 500-600 lb. coke or 30± gallons reduced oil, and yields about

10% metallic zinc and 1% blue powder--a mixture of finely-divided

metallic zinc and zinc oxide. About 60% of the zinc used in

desilverizing is recovered in a form to be used again. One man serves

2-4 retorts. The desilverized lead, which retains 0.6-0.7% zinc, has

to be refined before it is suited for industrial use. The operation is

carried on in a reverberatory furnace or in a kettle. In the

reverberatory furnace, similar to the one used in softening, the lead

is brought to a bright-red heat and air allowed to have free access.

The zinc and some lead are oxidized; part of the zinc passes off with

the fumes, part is dissolved by the litharge, forming a melted mixture

which is skimmed off and reduced in a blast-furnace or a reverberatory

smelting furnace. In the kettle covered with a hood the zinc is

oxidized by means of dry steam, and incidentally some lead by the air

which cannot be completely excluded. A yellowish powdery mixture of

zinc and lead oxides collects on the lead; it is skimmed off and sold

as paint. From the reverberatory furnace or the kettle the refined

lead is siphoned off into a storage (market) kettle after it has

cooled somewhat, and from this it is siphoned off into moulds placed

in a semi-circle on the floor. In the process the yield in metal,

based upon the charge in the kettle, is lead 99%, silver 100+%, gold

98-100%. The plus-silver is due to the fact that in assaying the base

bullion by cupellation, the silver lost by volatilization and

cupel-absorption is neglected. In the United States the cost of

desilverizing a ton base bullion is about $6.

_Properties of Lead._--Pure lead is a feebly lustrous bluish-white

metal, endowed with a characteristically high degree of softness and

plasticity, and almost entirely devoid of elasticity. Its breaking

strain is very small: a wire (1/10)th in. thick is ruptured by a charge

of about 30 lb. The specific gravity is 11.352 for ingot, and from

11.354 to 11.365 for sheet lead (water of 4°C. = 1). The expansion of

unit-length from 0°C. to to 100°C. is .002948 (Fizeau). The conductivity

for heat (Wiedemann and Franz) or electricity is 8.5, that of silver

being taken as 100. It melts at 327.7°C. (H. L. Callendar); at a

bright-red heat it perceptibly vapourizes, and boils at a temperature

between 1450° and 1600°. The specific heat is .0314 (Regnault). Lead

exposed to ordinary air is rapidly tarnished, but the thin dark film

formed is very slow in increasing. When kept fused in the presence of

air lead readily takes up oxygen, with the formation at first of a

dark-coloured scum, and then of monoxide PbO, the rate of oxidation

increasing with the temperature.

Water when absolutely pure has no action on lead, but in the presence of

air the lead is quickly attacked, with formation of the hydrate,

Pb(OH)2, which is appreciably soluble in water forming an alkaline

liquid. When carbonic acid is present the dissolved oxide is soon

precipitated as basic carbonate, so that the corrosion of the lead

becomes continuous. Since all soluble lead compounds are strong

cumulative poisons, danger is involved in using lead cisterns or pipes

in the distribution of _pure_ waters. The word "pure" is emphasized

because experience shows that the presence in a water of even small

proportions of calcium bicarbonate or sulphate prevents its action on

lead. All impurities do not act in a similar way. Ammonium nitrate and

nitrite, for instance, intensify the action of a water on lead. Even

pure waters, however, such as that of Loch Katrine (which forms the

Glasgow supply), act so slowly, at least on such lead pipes as have

already been in use for some time, that there is no danger in using

short lead service pipes even for them, if the taps are being constantly

used. Lead cisterns must be unhesitatingly condemned.

The presence of carbonic acid in a water does not affect its action on

lead. Aqueous non-oxidizing acids generally have little or no action on

lead in the absence of air. Dilute sulphuric acid (say an acid of 20%

H2SO4 or less) has no action on lead even when air is present, nor on

boiling. Strong acid does act, the more so the greater its concentration

and the higher its temperature. Pure lead is far more readily corroded

than a metal contaminated with 1% or even less of antimony or copper.

Boiling concentrated sulphuric acid converts lead into sulphate, with

evolution of sulphur dioxide. Dilute nitric acid readily dissolves the

metal, with formation of nitrate Pb(NO3)2.

_Lead Alloys._--Lead, unites readily with almost all other metals;

hence, and on account of its being used for the extraction of (for

instance) silver, its alchemistic name of _saturnus_. Of the alloys the

following may be named:--

_With Antimony._--Lead contaminated with small proportions of antimony

is more highly proof against sulphuric acid than the pure metal. An

alloy of 83 parts of lead and 17 of antimony is used as type metal;

other proportions are used, however, and other metals added besides

antimony (e.g. tin, bismuth) to give the alloy certain properties.

_Arsenic_ renders lead harder. An alloy made by addition of about

(1/56)th of arsenic has been used for making shot.

_Bismuth and Antimony._--An alloy consisting of 9 parts of lead, 2 of

antimony and 2 of bismuth is used for stereotype plates.

_Bismuth and Tin._--These triple alloys are noted for their low fusing

points. An alloy of 5 of lead, 8 of bismuth and 3 of tin fuses at

94.4°C, i.e. below the boiling-point of water (Rose's metal). An alloy

of 15 parts of bismuth, 8 of lead, 4 of tin and 3 of cadmium (Wood's

alloy) melts below 70°C.

_Tin_ unites with lead in any proportion with slight expansion, the

alloy fusing at a lower temperature than either component. It is used

largely for soldering.

"Pewter" (q.v.) may be said to be substantially an alloy of the same

two metals, but small quantities of copper, antimony and zinc are

frequently added.

_Compounds of Lead._

Lead generally functions as a divalent element of distinctly metallic

character, yielding a definite series of salts derived from the oxide

PbO. At the same time, however, it forms a number of compounds in which

it is most decidedly tetravalent; and thus it shows relations to carbon,

silicon, germanium and tin.

_Oxides._--Lead combines with oxygen to form five oxides, viz. Pb2O,

PbO, PbO2, Pb2O3 and Pb3O4. The _suboxide_, Pb2O, is the first product

of the oxidation of lead, and is also obtained as a black powder by

heating lead oxalate to 300° out of contact with air. It ignites when

heated in air with the formation of the monoxide; dilute acids convert

it into metallic lead and lead monoxide, the latter dissolving in the

acid. The _monoxide_, PbO, occurs in nature as the mineral _lead

ochre_. This oxide is produced by heating lead in contact with air and

removing the film of oxide as formed. It is manufactured in two forms,

known as "massicot" and "litharge." The former is produced at

temperatures below, the latter at temperatures above the fusing-point

of the oxide. The liquid litharge when allowed to cool solidifies into

a hard stone-like mass, which, however, when left to itself, soon

crumbles up into a heap of resplendent dark yellow scales known as

"flake litharge." "Buff" or "levigated litharge" is prepared by

grinding the larger pieces under water. Litharge is much used for the

preparation of lead salts, for the manufacture of oil varnishes, of

certain cements, and of lead plaster, and for other purposes. Massicot

is the raw material for the manufacture of "red lead" or "minium."

Lead monoxide is dimorphous, occurring as cubical dodecahedra and as

rhombic octahedra. Its specific gravity is about 9; it is sparingly

soluble in water, but readily dissolves in acids and molten alkalis. A

yellow and red modification have been described (_Zeit. anorg. Chem._,

1906, 50, p. 265). The corresponding _hydrate_, Pb(OH)2, is obtained

as a white crystalline precipitate by adding ammonia to a solution of

lead nitrate or acetate. It dissolves in an excess of alkali to form

_plumbites_ of the general formula Pb(OM)2. It absorbs carbon dioxide

from the air when moist. A hydrated oxide, 2PbO·H2O, is obtained when

a solution of the monoxide in potash is treated with carbon dioxide.

_Lead dioxide_, PbO2, also known as "puce oxide," occurs in nature as

the mineral plattnerite, and may be most conveniently prepared by

heating mixed solutions of lead acetate and bleaching powder until the

original precipitate blackens. The solution is filtered, the

precipitate well washed, and, generally, is put up in the form of a

paste in well-closed vessels. It is also obtained by passing chlorine

into a suspension of lead oxide or carbonate, or of magnesia and lead

sulphate, in water; or by treating the sesquioxide or red oxide with

nitric acid. The formation of lead dioxide by the electrolysis of a

lead solution, the anode being a lead plate coated with lead oxide or

sulphate and the cathode a lead plate, is the fundamental principle of

the storage cell (see ACCUMULATOR). Heating or exposure to sunlight

reduces it to the red oxide; it fires when ground with sulphur, and

oxidizes ammonia to nitric acid, with the simultaneous formation of

ammonium nitrate. It oxidizes a manganese salt (free from chlorine) in

the presence of nitric acid to a permanganate; this is a very delicate

test for manganese. It forms crystallizable salts with potassium and

calcium hydrates, and functions as a weak acid forming salts named

plumbates. The Kassner process for the manufacture of oxygen depends

upon the formation of calcium plumbate, Ca2PbO4, by heating a mixture

of lime and litharge in a current of air, decomposing this substance

into calcium carbonate and lead dioxide by heating in a current of

carbon dioxide, and then decomposing these compounds with the

evolution of carbon dioxide and oxygen by raising the temperature.

_Plumbic acid_, PbO(OH)2, is obtained as a bluish-black, lustrous body

of electrolysing an alkaline solution of lead sodium tartrate.

_Tetravalent Lead._--If a suspension of lead dichloride in

hydrochloric acid be treated with chlorine gas, a solution of lead

tetrachloride is obtained; by adding ammonium chloride ammonium

plumbichloride, (NH4)2PbCl6, is precipitated, which on treatment with

strong sulphuric acid yields _lead tetrachloride_, PbCl4, as a

translucent, yellow, highly refractive liquid. It freezes at -15° to a

yellowish crystalline mass; on heating it loses chlorine and forms

lead dichloride. With water it forms a hydrate, and ultimately

decomposes into lead dioxide and hydrochloric acid. It combines with

alkaline chlorides--potassium, rubidium and caesium--to form

crystalline _plumbichlorides_; it also forms a crystalline compound

with quinoline. By dissolving red lead, Pb3O4, in glacial acetic acid

and crystallizing the filtrate, colourless monoclinic prisms of lead

tetracetate, Pb(C2H3O2)4, are obtained. This salt gives the

corresponding chloride and fluoride with hydrochloric and hydrofluoric

acids, and the phosphate, Pb(HPO4)2, with phosphoric acid.

These salts are like those of tin; and the resemblance to this metal

is clearly enhanced by the study of the alkyl compounds. Here

compounds of divalent lead have not yet been obtained; by acting with

zinc ethide on lead chloride, _lead tetraethide_, Pb(C2H3)4, is

obtained, with the separation of metallic lead.

_Lead sesquioxide_, Pb2O3, is obtained as a reddish-yellow amorphous

powder by carefully adding sodium hypochlorite to a cold potash

solution of lead oxide, or by adding very dilute ammonia to a solution

of red lead in acetic acid. It is decomposed by acids into a mixture

of lead monoxide and dioxide, and may thus be regarded as lead

metaplumbate, PbPbO3. _Red lead_ or _triplumbic tetroxide_, Pb3O4, is

a scarlet crystalline powder of specific gravity 8.6-9.1, obtained by

roasting very finely divided pure massicot or lead carbonate; the

brightness of the colour depends in a great measure on the roasting.

Pliny mentions it under the name of _minium_, but it was confused with

cinnabar and the red arsenic sulphide; Dioscorides mentions its

preparation from white lead or lead carbonate. On heating it assumes a

finer colour, but then turns violet and finally black; regaining,

however, its original colour on cooling. On ignition, it loses oxygen

and forms litharge. Commercial red lead is frequently contaminated

with this oxide, which may, however, be removed by repeated digestion

with lead acetate. Its common adulterants are iron oxides, powdered

barytes and brick dust. Acids decompose it into lead dioxide and

monoxide, and the latter may or may not dissolve to form a salt; red

lead may, therefore, be regarded as _lead orthoplumbate_, Pb2PbO4. It

is chiefly used as a pigment and in the manufacture of flint glass.

_Lead chloride_, PbCl2, occurs in nature as the mineral cotunnite,

which crystallizes in the rhombic system, and is found in the

neighbourhood of volcanic craters. It is artificially obtained by

adding hydrochloric acid to a solution of lead salt, as a white

precipitate, little soluble in cold water, less so in dilute

hydrochloric acid, more so in the strong acid, and readily soluble in

hot water, from which on cooling, the excess of dissolved salt

separates out in silky rhombic needles. It melts at 485° and

solidifies on cooling to a translucent, horn-like mass; an early name

for it was _plumbum corneum_, horn lead. A basic chloride, Pb(OH)Cl,

was introduced in 1849 by Pattinson as a substitute for white lead.

Powdered galena is dissolved in hot hydrochloric acid, the solution

allowed to cool and the deposit of impure lead chloride washed with

cold water to remove iron and copper. The residue is then dissolved in

hot water, filtered, and the clear solution is mixed with very thin

milk of lime so adjusted that it takes out one-half of the chlorine of

the PbCl2. The oxychloride comes down as an amorphous white

precipitate. Another oxychloride, PbCl2·7PbO, known as "Cassel

yellow," was prepared by Vauquelin by fusing pure oxide, PbO, with

one-tenth of its weight of sal ammoniac. "Turner's yellow" or "patent

yellow" is another artificially prepared oxychloride, used as a

pigment. Mendipite and matlockite are mineral oxychlorides.

_Lead, fluoride_, PbF2, is a white powder obtained by precipitating a

lead salt with a soluble fluoride; it is sparingly soluble in water

but readily dissolves in hydrochloric and nitric acids. A

chloro-fluoride, PbClF, is obtained by adding sodium fluoride to a

solution of lead chloride. Lead bromide, PbBr2, a white solid, and

lead iodide, PbI2, a yellow solid, are prepared by precipitating a

lead salt with a soluble bromide or iodide; they resemble the chloride

in solubility.

_Lead carbonate_, PbCO3, occurs in nature as the mineral cerussite

(q.v.). It is produced by the addition of a solution of lead salt to

an excess of ammonium carbonate, as an almost insoluble white

precipitate. Of greater practical importance is a basic carbonate,

substantially 2PbCO3·Pb(OH)2, largely used as a white pigment under

the name of "white lead." This pigment is of great antiquity;

Theophrastus called it [Greek: psimythion], and prepared it by acting

on lead with vinegar, and Pliny, who called it _cerussa_, obtained it

by dissolving lead in vinegar and evaporating to dryness. It thus

appears that white lead and sugar of lead were undifferentiated. Geber

gave the preparation in a correct form, and T. O. Bergman proved its

composition. This pigment is manufactured by several methods. In the

old Dutch method, pieces of sheet lead are suspended in stoneware pots

so as to occupy the upper two-thirds of the vessels. A little vinegar

is poured into each pot; they are then covered with plates of sheet

lead, buried in horse-dung or spent tanner's bark, and left to

themselves for a considerable time. By the action of the acetic acid

and atmospheric oxygen, the lead is converted superficially into a

basic acetate, which is at once decomposed by the carbon dioxide, with

formation of white lead and acetic acid, which latter then acts _de

novo_. After a month or so the plates are converted to a more or less

considerable depth into crusts of white lead. These are knocked off,

ground up with water, freed from metal-particles by elutriation, and

the paste of white lead is allowed to set and dry in small conical

forms. The German method differs from the Dutch inasmuch as the lead

is suspended in a large chamber heated by ordinary means, and there

exposed to the simultaneous action of vapour of aqueous acetic acid

and of carbon dioxide. Another process depends upon the formation of

lead chloride by grinding together litharge with salt and water, and

then treating the alkaline fluid with carbon dioxide until it is

neutral. White lead is an earthy, amorphous powder. The inferior

varieties of commercial "white lead" are produced by mixing the

genuine article with more or less of finely powdered heavy spar or

occasionally zinc-white (ZnO). Venetian white, Hamburg white and Dutch

white are mixtures of one part of white lead with one, two and three

parts of barium sulphate respectively.

_Lead sulphide_, PbS, occurs in nature as the mineral galena (q.v.),

and constitutes the most valuable ore of lead. It may be artificially

prepared by leading sulphur vapour over lead, by fusing litharge with

sulphur, or, as a black precipitate, by passing sulphuretted hydrogen

into a solution of a lead salt. It dissolves in strong nitric acid

with the formation of the nitrate and sulphate, and also in hot

concentrated hydrochloric acid.

_Lead sulphate_, PbSO4, occurs in nature as the mineral anglesite

(q.v.), and may be prepared by the addition of sulphuric acid to

solutions of lead salts, as a white precipitate almost insoluble in

water (1 in 21,739), less soluble still in dilute sulphuric acid (1 in

36,504) and insoluble in alcohol. Ammonium sulphide blackens it, and

it is coluble in solution of ammonium acetate, which distinguishes it

from barium sulphate. Strong sulphuric acid dissolves it, forming an

acid salt, Pb(HSO4)2, which is hydrolysed by adding water, the normal

sulphate being precipitated; hence the milkiness exhibited by samples

of oil of vitriol on dilution.

_Lead nitrate_, Pb(NO3)2, is obtained by dissolving the metal or oxide

in aqueous nitric acid; it forms white crystals, difficultly soluble

in cold water, readily in hot water and almost insoluble in strong

nitric acid. It was mentioned by Libavius, who named it _calx plumb

dulcis_. It is decomposed by heat into oxide, nitrogen peroxide and

oxygen; and is used for the manufacture of fusees and other

deflagrating compounds, and also for preparing mordants in the dyeing

and calico-printing industries. Basic nitrates, e.g. Pb(NO3)OH,

Pb3O(OH)2(NO3)2, Pb3O2(OH)NO3, &c., have been described.

_Lead Phosphates._--The normal ortho-phosphate, Pb3(PO4)2, is a white

precipitate obtained by adding sodium phosphate to lead acetate; the

acid phosphate, PbHPO4, is produced by precipitating a boiling

solution of lead nitrate with phosphoric acid; the pyrophosphate and

meta-phosphate are similar white precipitates.

_Lead Borates._--By fusing litharge with boron trioxide, glasses of a

composition varying with the proportions of the mixture are obtained;

some of these are used in the manufacture of glass. The borate,

Pb2B6O11·4H2O, is obtained as a white precipitate by adding borax to a

lead salt; this on heating with strong ammonia gives PbB2O4·H2·O,

which, in turn, when boiled with a solution of boric acid, gives

PbB4O7·4H2O.

_Lead silicates_ are obtained as glasses by fusing litharge with

silica; they play a considerable part in the manufacture of the lead

glasses (see GLASS).

_Lead chromate_, PbCrO4, is prepared industrially as a yellow pigment,

chrome yellow, by precipitating sugar of lead solution with potassium

bichromate. The beautiful yellow precipitate is little soluble in

dilute nitric acid, but soluble in caustic potash. The vermilion-like

pigment which occurs in commerce as "chrome-red" is a basic chromate,

Pb2CrO5, prepared by treating recently precipitated normal chromate

with a properly adjusted proportion of caustic soda, or by boiling it

with normal (yellow) potassium chromate.

_Lead acetate_, Pb(C2H3O2)2·3H2O (called "sugar" of lead, on account

of its sweetish taste), is manufactured by dissolving massicot in

aqueous acetic acid. It forms colourless transparent crystals, soluble

in one and a half parts of cold water and in eight parts of alcohol,

which on exposure to ordinary air become opaque through absorption of

carbonic acid, which forms a crust of basic carbonate. An aqueous

solution readily dissolves lead oxide, with formation of a strongly

alkaline solution containing basic acetates (_Acetum Plumbi_ or

_Saturni_). When carbon dioxide is passed into this solution the whole

of the added oxide, and even part of the oxide of the normal salt, is

precipitated as a basic carbonate chemically similar, but not quite

equivalent as a pigment, to white lead.

_Analysis._--When mixed with sodium carbonate and heated on charcoal in

the reducing flame lead salts yield malleable globules of metal and a

yellow oxide-ring. Solutions of lead salts (colourless in the absence of

coloured acids) are characterized by their behaviour to hydrochloric

acid, sulphuric acid and potassium chromate. But the most delicate

precipitant for lead is sulphuretted hydrogen, which produces a black

precipitate of lead sulphide, insoluble in cold dilute nitric acid, less

so in cold hydrochloric, and easily decomposed by hot hydrochloric acid

with formation of the characteristic chloride. The atomic weight,

determined by G. P. Baxter and J. H. Wilson (_J. Amer. Chem. Soc._,

1908, 30, p. 187) by analysing the chloride, is 270.190 (O = 16).

_Pharmacology and Therapeutics._

The metal itself is not used in medicine. The chief pharmacopoeial salts

are: (1) _Plumbi oxidum_ (lead oxide), litharge. It is not used

internally, but from it is made _Emplastrum Plumbi_ (diachylon plaster),

which is an oleate of lead and is contained in emplastrum hydrargeri,

emplastrum plumbi iodidi, emplastrum resinae, emplastrum saponis. (2)

_Plumbi Acetas_ (sugar of lead), dose 1 to 5 grains. From this salt are

made the following preparations: (a) _Pilula Plumbi cum Opio_, the

strength of the opium in it being 1 in 8, dose 2 to 4 grains; (b)

_Suppositoria Plumbi composita_, containing lead acetate, opium and oil

of theobroma, there being one grain of opium in each suppository; (c)

_Unguentum Plumbi Acetatis_; (d) _Liquor Plumbi Subacetatis Fortior_,

Goulard's extract, strength 24% of the subacetate; this again has a

sub-preparation, the _Liquor Plumbi Subacetatis Dilutis_, called

Goulard's water or Goulard's lotion, containing 1 part in 80 of the

strong extract; (e) _Glycerinum Plumbi Subacetatis_, from which is made

the _Unguentum Glycerini Plumbi Subacetatis_. (3) _Plumbi Carbonas_,

white lead, a mixture of the carbonate and the hydrate, a heavy white

powder insoluble in water; it is not used internally, but from it is

made _Unguentum Plumbi Carbonatis_, strength 1 in 10 parts of paraffin

ointment. (4) _Plumbi Iodidium_, a heavy bright yellow powder not used

internally. From it are made (a) _Emplastrum Plumbi Iodidi_, and (b)

_Unguentum Plumbi Iodidi_. The strength of each is 1 in 10.

Applied externally lead salts have practically no action upon the

unbroken skin, but applied to sores, ulcers or any exposed mucous

membranes they coagulate the albumen in the tissues themselves and

contract the small vessels. They are very astringent, haemostatic and

sedative; the strong solution of the subacetate is powerfully caustic

and is rarely used undiluted. Lead salts are applied as lotions in

conditions where a sedative astringent effect is desired, as in weeping

eczema; in many varieties of chronic ulceration; and as an injection for

various inflammatory discharges from the vagina, ear and urethra, the

Liquor Plumbi Subacetatis Dilutum being the one employed. The sedative

effect of lead lotion in pruritus is well known. Internally lead has an

astringent action on the mucous membranes, causing a sensation of

dryness; the dilute solution of the subacetate forms an effective gargle

in tonsillitis. The chief use of the preparations of lead, however, is

as an astringent in acute diarrhoea, particularly if ulceration be

present, when it is usefully given in combination with opium in the form

of the Pilula Plumbi cum Opio. It is useful in haemorrhage from a

gastric ulcer or in haemorrhage from the intestine. Lead salts usually

produce constipation, and lead is an active ecbolic. Lead is said to

enter the blood as an albuminate in which form it is deposited in the

tissues. As a rule the soluble salts if taken in sufficient quantities

produce acute poisoning, and the insoluble salts chronic plumbism. The

symptoms of acute poisoning are pain and diarrhoea, owing to the setting

up of an active gastro-enteritis, the foeces being black (due to the

formation of a sulphide of lead), thirst, cramps in the legs and

muscular twitchings, with torpor, collapse, convulsions and coma. The

treatment is the prompt use of emetics, or the stomach should be washed

out, and large doses of sodium or magnesium sulphate given in order to

form an insoluble sulphate. Stimulants, warmth and opium may be

required. For an account of chronic plumbism see LEAD POISONING.

AUTHORITIES.--For the history of lead see W. H. Pulsifer, _Notes for a

History of Lead_ (1888); B. Neumann, _Die Metalle_ (1904); A. Rossing,

_Geschichte der Metalle_ (1901). For the chemistry see H. Roscoe and

C. Schorlemmer, _Treatise on Inorganic Chemistry_, vol. ii. (1897); H.

Moissan, _Traité de chimie minerale_; O. Dammer, _Handbuch der

anorganischen Chemie_. For the metallurgy see J. Percy, _The

Metallurgy of Lead_ (London, 1870); H. F. Collins, _The Metallurgy of

Lead and Silver_ (London, 1899), part i. "Lead"; H. O. Hofmann, _The

Metallurgy of Lead_ (6th ed., New York, 1901); W. R. Ingalls, _Lead

Smelting and Refining_ (1906); A. G. Betts, _Lead Refining by

Electrolysis_ (1908); M. Eissler, _The Metallurgy of Argentiferous

Silver_. _The Mineral Industry_, begun in 1892, annually records the

progress made in lead smelting.

LEADER, BENJAMIN WILLIAMS (1831- ), English painter, the son of E.

Leader Williams, an engineer, received his art education first at the

Worcester School of Design and later in the schools of the Royal

Academy. He began to exhibit at the Academy in 1854, was elected A.R.A.

in 1883 and R.A. in 1898, and became exceedingly popular as a painter of

landscape. His subjects are attractive and skilfully composed. He was

awarded a gold medal at the Paris Exhibition in 1889, and was made a

knight of the Legion of Honour. One of his pictures, "The Valley of the

Llugwy," is in the National Gallery of British Art.

See _The Life and Work of B. W. Leader, R.A._, by Lewis Lusk, _Art

Journal_ Office (1901).

LEADHILLITE, a rare mineral consisting of basic lead sulphato-carbonate,

Pb4SO4(CO3)2(OH)2. Crystals have usually the form of six-sided plates

(fig. 1) or sometimes of acute rhombohedra (fig. 2); they have a perfect

basal cleavage (parallel to P in fig. 1) on which the lustre is strongly

pearly; they are usually white and translucent. The hardness is 2.5 and

the sp. gr. 6.26-6.44. The crystallographic and optical characters point

to the existence of three distinct kinds of leadhillite, which are,

however, identical in external appearance and may even occur intergrown

together in the same crystal: (a) monoclinic with an optic axial angle

of 20°; (b) rhombohedral (fig. 2) and optically uniaxial; (c)

orthorhombic (fig. 1) with an optic axial angle of 72¾°. The first of

these is the more common kind, and the second has long been known under

the name susannite. The fact that the published analyses of leadhillite

vary somewhat from the formula given above suggests that these three

kinds may also be chemically distinct.

[Illustration: FIG. 1.]

[Illustration: FIG. 2.]

Leadhillite is a mineral of secondary origin, occurring with cerussite,

anglesite, &c., in the oxidized portions of lead-bearing lodes; it has

also been found in weathered lead slags left by the Romans. It has been

found most abundantly in the Susanna mine at Leadhills in Scotland

(hence the names leadhillite and susannite). Good crystals have also

been found at Red Gill in Cumberland and at Granby in Missouri. Crystals

from Sardinia have been called maxite. (L. J. S.)

LEADHILLS, a village of Lanarkshire, Scotland, 5¾ m. W.S.W. of Elvanfoot

station on the Caledonian Railway Company's main line from Glasgow to

the south. Pop. (1901) 835. It is the highest village in Scotland, lying

1301 ft. above sea-level, near the source of Glengonner Water, an

affluent of the Clyde. It is served by a light railway. Lead and silver

have been mined here and at Wanlockhead, 1½ m. S.W., for many

centuries--according to some authorities even in Roman days. Gold was

discovered in the reign of James IV., but though it is said then to have

provided employment for 300 persons, its mining has long ceased to be

profitable. The village is neat and well built, and contains a masonic

hall and library, the latter founded by the miners about the middle of

the 18th century. Allan Ramsay, the poet, and William Symington

(1763-1831), one of the earliest adaptors of the steam engine to the

purposes of navigation, were born at Leadhills.

LEAD POISONING, or PLUMBISM, a "disease of occupations," which is itself

the cause of organic disease, particularly of the nervous and urinary

systems. The workpeople affected are principally those engaged in

potteries where lead-glaze is used; but other industries in which health

is similarly affected are file-making, house-painting and glazing,

glass-making, copper-working, coach-making, plumbing and gasfitting,

printing, cutlery, and generally those occupations in which lead is

concerned.

The symptoms of chronic lead poisoning vary within very wide limits,

from colic and constipation up to total blindness, paralysis,

convulsions and death. They are thus described by Dr J. T. Arlidge

(_Diseases of Occupations_):--

The poison finds its way gradually into the whole mass of the

circulating blood, and exerts its effects mainly on the nervous

system, paralysing nerve-force and with it muscular power. Its victims

become of a sallow-waxy hue; the functions of the stomach and bowels

are deranged, appetite fails and painful colic with constipation

supervenes. The loss of power is generally shown first in the fingers,

hands and wrists, and the condition known as "wrist-drop" soon

follows, rendering the victim useless for work. The palsy will extend

to the shoulders, and after no long time to the legs also. Other

organs frequently involved are the kidneys, the tissue of which

becomes permanently damaged; whilst the sight is weakened or even

lost.

Dr M'Aldowie, senior physician to the North Staffordshire Infirmary, has

stated that "in the pottery trade lead is very slow in producing serious

effects compared with certain other industries." In his experience the

average period of working in lead before serious lesions manifest

themselves is 18 years for females and 22½ years for males. But some

individuals fall victims to the worst forms of plumbism after a few

months' or even weeks' exposure to the danger. Young persons are more

readily affected than those of mature age, and women more than men. In

addition, there seems to be an element of personal susceptibility, the

nature of which is not understood. Some persons "work in the lead" for

twenty, forty or fifty years without the slightest ill effects; others

have attacks whenever they are brought into contact with it. Possibly

the difference is due to the general state of health; robust persons

resist the poison successfully, those with impoverished blood and feeble

constitution are mastered by it. Lead enters the body chiefly through

the nose and mouth, being inspired in the form of dust or swallowed with

food eaten with unwashed hands. It is very apt to get under the nails,

and is possibly absorbed in this way through the skin. Personal care and

cleanliness are therefore of the greatest importance. A factory surgeon

of great experience in the English Potteries has stated that seventeen

out of twenty cases of lead-poisoning in the china and earthenware

industry are due to carelessness (_The Times_, 8th October 1898).

The Home Office in England has from time to time made special rules for

workshops and workpeople, with the object of minimizing or preventing

the occurrence of lead-poisoning; and in 1895 notification of cases was

made compulsory. The health of workpeople in the Potteries was the

subject of a special inquiry by a scientific committee in 1893. The

committee stated that "the general truth that the potteries occupation

is one fraught with injury to health and life is beyond dispute," and

that "the ill effects of the trade are referable to two chief

causes--namely, dust and the poison of lead." Of these the inhalation of

clay and flint dust was the more important. It led to bronchitis,

pulmonary tuberculosis and pneumonia, which were the most prevalent

disorders among potters, and responsible for 70% of the mortality. That

from lead the committee did not attempt to estimate, but they found that

plumbism was less prevalent than in past times, and expressed the

opinion "that a large part of the mortality from lead poisoning is

avoidable; although it must always be borne in mind that no arrangements

or rules, with regard to the work itself, can entirely obviate the

effects of the poison to which workers are exposed, because so much

depends upon the individual and the observance of personal care and

cleanliness." They recommended the adoption of certain special rules in

the workshops, with the objects of protecting young persons from the

lead, of minimizing the evils of dust, and of promoting cleanliness,

particularly in regard to meals. Some of these recommendations were

adopted and applied with good results. With regard to the suggestion

that "only leadless glazes should be used on earthenware," they did not

"see any immediate prospect of such glazes becoming universally

applicable to pottery manufacture," and therefore turned their attention

to the question of "fritting" the lead.

It may be explained that lead is used in china and earthenware to give

the external glaze which renders the naturally porous ware watertight.

Both "white" and "red" lead are used. The lead is added to other

ingredients, which have been "fritted" or fused together and then

ground very fine in water, making a thick creamy liquid into which the

articles are dipped. After dipping the glaze dries quickly, and on

being "fired" in the kiln it becomes fused by the heat into the

familiar glassy surface. In the manufacture of ware with enamelled

colours, glaze is mixed with the pigment to form a flux, and such

colours are used either moist or in the form of a dry powder.

"Fritting" the lead means mixing it with the other ingredients of the

glaze beforehand and fusing them all together under great heat into a

kind of rough glass, which is then ground to make the glaze. Treated

in this way the lead combines with the other ingredients and becomes

less soluble, and therefore less dangerous, than when added afterwards

in the raw state. The committee (1893) thought it "reasonable to

suppose that the fritting of lead might ultimately be found

universally practicable," but declared that though fritting "no doubt

diminishes the danger of lead-poisoning," they "could not regard all

fritts as equally innocuous."

In the annual report of the chief inspector of factories for 1897, it

was stated that there had been "material improvement in dust conditions"

in the potting industry, but "of lead-poisoning unfortunately the same

could not be said, the number of grave cases reported, and particularly

cases of blindness, having ominously increased of late." This appears to

have been largely due to the erroneous inclusion among potting processes

of "litho-transfer making," a colour industry in which girls are

employed. New special rules were imposed in 1899 prohibiting the

employment of persons under fifteen in the dangerous processes, ordering

a monthly examination of all women and young persons working in lead by

the certifying surgeon, with power to suspend those showing symptoms of

poisoning, and providing for the more effectual removal of dust and the

better enforcement of cleanliness. At the same time a scientific inquiry

was ordered into the practicability of dispensing with lead in glazes or

of substituting fritted compounds for the raw carbonate. The scientific

experts reported in 1899, recommending that the use of raw lead should

be absolutely prohibited, and expressing the opinion that the greater

amount of earthenware could be successfully glazed without any lead.

These views were in advance of the opinions held by practical potters,

and met with a good deal of opposition. By certain manufacturers

considerable progress had been made in diminishing the use of raw lead

and towards the discovery of satisfactory leadless glazes; but it is a

long step from individual experiments to the wholesale compulsory

revolution of the processes of manufacture in so large and varied an

industry, and in the face of foreign competitors hampered by no such

regulations. The materials used by each manufacturer have been arrived

at by a long process of experience, and they are such as to suit the

particular goods he supplies for his particular market. It is therefore

difficult to apply a uniform rule without jeopardizing the prosperity of

the industry, which supports a population of 250,000 in the Potteries

alone. However, the bulk of the manufacturers agreed to give up the use

of raw lead, and to fritt all their glazes in future, time being allowed

to effect the change of process; but they declined to be bound to any

particular composition of glaze for the reasons indicated.

In 1901 the Home Office brought forward a new set of special rules. Most

of these were framed to strengthen the provisions for securing

cleanliness, removing dust, &c., and were accepted with a few

modifications. But the question of making even more stringent

regulations, even to the extent of making the use of lead-glaze illegal

altogether, was still agitated; and in 1906 the Home Office again

appointed an expert committee to reinvestigate the subject. They

reported in 1910, and made various recommendations in detail for

strengthening the existing regulations; but while encouraging the use of

leadless glaze in certain sorts of common ceramic ware, they pointed out

that, without the use of lead, certain other sorts could either not be

made at all or only at a cost or sacrifice of quality which would entail

the loss of important markets.

In 1908 Dr Collis made an inquiry into the increase of plumbism in

connexion with the smelting of metals, and he considered the increase

in the cases of poisoning reported to be due to the third schedule of

the Workmen's Compensation Act, (1) by causing the prevalence of

pre-existing plumbism to come to light, (2) by the tendency this

fostered to replace men suspected of lead impregnation by new hands

amongst whom the incidence is necessarily greater.

LEADVILLE, a city and the county seat of Lake county, Colorado, U.S.A.,

one of the highest (mean elevation c. 10,150 ft.) and most celebrated

mining "camps" of the world. Pop. (1900) 12,455, of whom 3802 were

foreign-born; (1910 census) 7508. It is served by the Denver & Rio

Grande, the Colorado & Southern and the Colorado Midland railways. It

lies amid towering mountains on a terrace of the western flank of the

Mosquito Range at the head of the valley of the Arkansas river, where

the river cuts the valley between the Mosquito and the Sawatch

(Saguache) ranges. Among the peaks in the immediate environs are Mt.

Massive (14,424 ft., the highest in the state) and Elbert Peak (14,421

ft.). There is a United States fish hatchery at the foot of Mt. Massive.

In the spring of 1860 placer gold was discovered in California Gulch,

and by July 1860 Oro City had probably 10,000 inhabitants. In five years

the total yield was more than $5,000,000; then it diminished, and Oro

City shrank to a few hundred inhabitants. This settlement was within the

present limits of Leadville. In 1876 the output of the mines was about

$20,000. During sixteen years "heavy sands" and great boulders that

obstructed the placer fields had been moved thoughtlessly to one side.

These boulders were from enormous lead carbonate deposits extremely rich

in silver. The discovery of these deposits was made on the hills at the

edge of Leadville. The first building was erected in June 1877; in

December there were several hundred miners, in January the town was

organized and named; at the end of 1879 there were, it is said, 35,000

inhabitants. Leadville was already a chartered city, with the usual

organization and all public facilities. In 1880 it was reached by the

Denver & Rio Grande railway. In early years Leadville was one of the

most turbulent, picturesque and in all ways extraordinary, of the mining

camps of the West. The value of the output from 1879 to 1889 totalled

$147,834,186, including one-fifth of the silver production and a third

of the lead consumption of the country. The decline in the price of

silver, culminating with the closing of the India mints and the repeal

of the Sherman Law in 1893, threatened Leadville's future. But the

source of the gold of the old placers was found in 1892. From that year

to 1899 the gold product rose from $262,692 to $2,183,332. From 1879 to

1900 the camp yielded $250,000,000 (as compared with $48,000,000 of gold

and silver in five years from the Comstock, Nevada, lode; and

$60,000,000 and 225,000 tons of lead, in fourteen years, from the

Eureka, Nevada, mines). Before 1898 the production of zinc was

unimportant, but in 1906 it was more valuable than that of silver and

gold combined. This increased output is a result of the establishment of

concentrating mills, in which the zinc content is raised from 18 or 20%

in the raw ores to 25 or 45% in the concentrates. In 1904, per ton of

Lake county ore, zinc was valued at $6.93, silver at $4.16, lead at

$3.85, gold at $1.77 and copper at $.66. The copper mined at Leadville

amounted to about one-third the total mined in the state in 1906. Iron

and manganese have been produced here, and in 1906 Leadville was the

only place in the United States known to have produced bismuth. There

were two famous labour strikes in the "diggings" in 1879 and 1896. The

latter attracted national attention; it lasted from the 19th of June

1896 to the 9th of March 1897, when the miners, being practically

starved out, declared the strike off. There had been a riot on the 21st

of September 1896 and militia guarded the mines for months afterwards.

In January 1897 the mines on Carbonate Hill were flooded after the

removal of their pumps. This strike closed many mines, which were not

opened for several years. Leadville stocks are never on the exchange,

and "flotation" and "promotion" have been almost unknown.

The ores of the Leadville District occur in a blue limestone formation

overlaid by porphyry, and are in the form of heavy sulphides,

containing copper, gold, silver, lead and zinc; oxides containing

iron, manganese and small amounts of silver and lead; and siliceous

ores, containing much silver and a little lead and gold. The best

grade of ores usually consists of a mixture of sulphides, with some

native gold. Nowhere have more wonderful advances in mining been

apparent--in the size and character of furnaces and pumps; the

development of local smelter supplies; the fall in the cost of coal,

of explosives and other mine supplies; the development of railways and

diminution of freight expenses; and the general improvement of

economic and scientific methods--than at Leadville since 1880. The

increase of output more than doubled from 1890 to 1900, and many ores

once far too low in grade for working now yield sure profits. The

Leadville smelters in 1900 had a capacity of 35,000 tons monthly;

about as much more local ore being treated at Denver, Pueblo and other

places.

See S. F. Emmons, _Geology and Mining Industry of Leadville,

Colorado_, monograph United States Geological Survey, vol. 12 (1886),

and with J. D. Irving, _The Downtown District of Leadville, Colorado_,

Bulletin 320, United States Geological Survey (1907), particularly for

the discussion of the origin of the ores of the region.

LEAF (O. Eng. _léaf_, cf. Dutch _loof_, Ger. _Laub_, Swed. _löf_, &c.;

possibly to be referred to the root seen in Gr. [Greek: lepein], to

peel, strip), the name given in popular language to all the green

expanded organs borne upon an axis, and so applied to similar objects,

such as a thin sheet of metal, a hinged flap of a table, the page of a

book, &c. Investigation has shown that many other parts of a plant which

externally appear very different from ordinary leaves are, in their

essential particulars, very similar to them, and are in fact their

morphological equivalents. Such are the scales of a bulb, and the

various parts of the flower, and assuming that the structure ordinarily

termed a leaf is the typical form, these other structures were

designated changed or metamorphosed leaves, a somewhat misleading

interpretation. All structures morphologically equivalent with the leaf

are now included under the general term _phyllome_ (leaf-structure).

[Illustration: From Strasburger's Lehrbuch der Botanik by permission of

Gustav Fischer.

FIG. 1.--Apex of a shoot showing origin of leaves: f, leaf rudiment; g,

rudiment of an axillary bud.]

Leaves are produced as lateral outgrowths of the stem in definite

succession below the apex. This character, common to all leaves,

distinguishes them from other organs. In the higher plants we can easily

recognize the distinction between stem and leaf. Amongst the lower

plants, however, it is found that a demarcation into stem and leaf is

impossible, but that there is a structure which partakes of the

characters of both--such is a _thallus_. The leaves always arise from

the outer portion of the primary meristem of the plant, and the tissues

of the leaf are continuous with those of the stem. Every leaf originates

as a simple cellular papilla (fig. 1), which consists of a development

from the cortical layers covered by epidermis; and as growth proceeds,

the fibro-vascular bundles of the stem are continued outwards, and

finally expand and terminate in the leaf. The increase in length of the

leaf by growth at the apex is usually of a limited nature. In some

ferns, however, there seems to be a provision for indefinite terminal

growth, while in others this growth is periodically interrupted. It not

unfrequently happens, especially amongst Monocotyledons, that after

growth at the apex has ceased, it is continued at the base of the leaf,

and in this way the length may be much increased. Amongst Dicotyledons

this is very rare. In all cases the dimensions of the leaf are enlarged

by interstitial growth of its parts.

Structure of leaves.

The simplest leaf is found in some mosses, where it consists of a single

layer of cells. The typical foliage leaf consists of several layers, and

amongst vascular plants is distinguishable into an outer layer

(_epidermis_) and a central tissue (_parenchyma_) with fibro-vascular

bundles distributed through it.

[Illustration: FIG. 2.--Section of a Melon leaf, perpendicular to the

surface.

es, Upper epidermis.

ei, Lower epidermis.

p, Hairs.

st, Stomata.

ps, Upper (palisade) layers of parenchymatous cells.

pi, Lower (spongy) layers of parenchymatous cells.

m, Air-spaces connected with stomata.

l, Air-spaces between the loose cells in the spongy parenchyma.

fv, Bundles of fibro-vascular tissue.]

The _epidermis_ (fig. 2, es, ei), composed of cells more or less

compressed, has usually a different structure and aspect on the two

surfaces of the leaf. The cells of the epidermis are very closely

united laterally and contain no green colouring matter (chlorophyll)

except in the pair of cells--guard-cells--which bound the stomata. The

outer wall, especially of the upper epidermis, has a tough outer layer

or cuticle which renders it impervious to water. The epidermis is

continuous except where stomata or spaces bounded by specialized cells

communicate with intercellular spaces in the interior of the leaf. It

is chiefly on the epidermis of the lower surface (fig. 2, ei) that

stomata, st, are produced, and it is there also that hairs, p, usually

occur. The lower epidermis is often of a dull or pale-green colour,

soft and easily detached. The upper epidermis is frequently smooth and

shining, and sometimes becomes very hard and dense. Many tropical

plants present on the upper surface of their leaves several layers of

compressed cells beneath the epidermis which serve for storage of

water and are known as aqueous tissue. In leaves which float upon the

surface of the water, as those of the water-lily, the upper epidermis

alone possesses stomata.

The _parenchyma_ of the leaf is the cellular tissue enclosed within

the epidermis and surrounding the vessels (fig. 2, ps, pi). It is

known as _mesophyll_, and is formed of two distinct series of cells,

each containing the green chlorophyll-granules, but differing in form

and arrangement. Below the epidermis of the upper side of the leaf

there are one or two layers of cells, elongated at right angles to the

leaf surface (fig. 2, ps), and applied so closely to each other as to

leave only small intercellular spaces, except where stomata happen to

be present (fig. 2, m); they form the palisade tissue. On the other

side of the leaf the cells are irregular, often branched, and are

arranged more or less horizontally (fig. 2, pi), leaving air-spaces

between them, l, which communicate with stomata; on this account the

tissue has received the name of spongy. In leaves having a very firm

texture, as those of Coniferae and Cycadaceae, the cells of the

parenchyma immediately beneath the epidermis are very much thickened

and elongated in a direction parallel to the surface of the leaf, so

as to be fibre-like. These constitute a hypodermal layer, beneath

which the chlorophyll cells of the parenchyma are densely packed

together, and are elongated in a direction vertical to the surface of

the leaf, forming the palisade tissue. The form and arrangement of the

cells, however, depend much on the nature of the plant, and its

exposure to light and air. Sometimes the arrangement of the cells on

both sides of the leaf is similar, as occurs in leaves which have

their edges presented to the sky. In very succulent plants the cells

form a compact mass, and those in the centre are often colourless. In

some cases the cellular tissue is deficient at certain points, giving

rise to distinct holes in the leaf, as in _Monstera Adansonii_. The

fibro-vascular system in the leaf constitutes the _venation_. The

fibro-vascular bundles from the stem bend out into the leaf, and are

there arranged in a definite manner. In _skeleton leaves_, or leaves

in which the parenchyma is removed, this arrangement is well seen. In

some leaves, as in the barberry, the veins are hardened, producing

spines without any parenchyma. The hardening of the extremities of the

fibro-vascular tissue is the cause of the spiny margin of many leaves,

such as the holly, of the sharp-pointed leaves of madder, and of

mucronate leaves, or those having a blunt end with a hard projection

in the centre.

The form and arrangement of the parts of a typical foliage leaf are

intimately associated with the part played by the leaf in the life of

the plant. The flat surface is spread to allow the maximum amount of

sunlight to fall upon it, as it is by the absorption of energy from the

sun's rays by means of the chlorophyll contained in the cells of the

leaf that the building up of plant food is rendered possible; this

process is known as photo-synthesis; the first stage is the combination

of carbon dioxide, absorbed from the air taken in through the stomata

into the living cells of the leaf, with water which is brought into the

leaf by the wood-vessels. The wood-vessels form part of the

fibro-vascular bundles or veins of the leaf and are continuous

throughout the leaf-stalk and stem with the root by which water is

absorbed from the soil. The palisade layers of the mesophyll contain the

larger number of chlorophyll grains (or corpuscles) while the absorption

of carbon dioxide is carried on chiefly through the lower epidermis

which is generally much richer in stomata. The water taken up by the

root from the soil contains nitrogenous and mineral salts which combine

with the first product of photo-synthesis--a carbohydrate--to form more

complicated nitrogen-containing food substances of a proteid nature;

these are then distributed by other elements of the vascular bundles

(the _phloem_) through the leaf to the stem and so throughout the plant

to wherever growth or development is going on. A large proportion of the

water which ascends to the leaf acts merely as a carrier for the other

raw food materials and is got rid of from the leaf in the form of water

vapour through the stomata--this process is known as _transpiration_.

Hence the extended surface of the leaf exposing a large area to light

and air is eminently adapted for the carrying out of the process of

photo-synthesis and transpiration. The arrangement of the leaves on the

stem and branches (see _Phyllotaxy_, below) is such as to prevent the

upper leaves shading the lower, and the shape of the leaf serves towards

the same end--the disposition of leaves on a branch or stem is often

seen to form a "mosaic," each leaf fitting into the space between

neighbouring leaves and the branch on which they are borne without

overlapping.

Submerged leaves, or leaves which are developed under water, differ in

structure from aerial leaves. They have usually no fibro-vascular

system, but consist of a congeries of cells, which sometimes become

elongated and compressed so as to resemble veins. They have a layer of

compact cells on their surface, but no true epidermis, and no stomata.

Their internal structure consists of cells, disposed irregularly, and

sometimes leaving spaces which are filled with air for the purpose of

floating the leaf. When exposed to the air these leaves easily part with

their moisture, and become shrivelled and dry. In some cases there is

only a network of filament-like cells, the spaces between which are not

filled with parenchyma, giving a skeleton appearance to the leaf, as in

_Ouvirandra fenestralis_ (Lattice plant).

A leaf, whether aerial or submerged, generally consists of a flat

expanded portion, called the _blade_, or _lamina_, of a narrower portion

called the _petiole_ or _stalk_, and sometimes of a portion at the base

of the petiole, which forms a _sheath_ or _vagina_ (fig. 5, s), or is

developed in the form of outgrowths, called _stipules_ (fig. 24, s).

All these portions are not always present. The sheathing or stipulary

portion is frequently wanting. When a leaf has a distinct stalk it is

_petiolate_; when it has none, it is _sessile_, and if in this case it

embraces the stem it is said to be _amplexicaul_. The part of the leaf

next the petiole or the axis is the _base_, while the opposite extremity

is the _apex_. The leaf is usually flattened and expanded horizontally,

i.e. at right angles to the longitudinal axis of the shoot, so that the

upper face is directed towards the heavens, and the lower towards the

earth. In some cases leaves, as in Iris, or leaf-like petioles, as in

Australian acacias and eucalypti, have their plane of expansion parallel

to the axis of the shoot, there is then no distinction into an upper and

a lower face, but the two sides are developed alike; or the leaf may

have a cylindrical or polyhedral form, as in mesembryanthemum. The upper

angle formed between the leaf and the stem is called its _axil_; it is

there that leaf-buds are normally developed. The leaf is sometimes

articulated with the stem, and when it falls off a _scar_ remains; at

other times it is continuous with it, and then decays, while still

attached to the axis. In their early state all leaves are continuous

with the stem, and it is only in their after growth that articulations

are formed. When leaves fall off annually they are called _deciduous_;

when they remain for two or more years they are _persistent_, and the

plant is _evergreen_. The laminar portion of a leaf is occasionally

articulated with the petiole, as in the orange, and a joint at times

exists between the vaginal or stipulary portion and the petiole.

[Illustration: FIG. 3.--Leaf of Elm (_Ulmus_). Reticulated venation;

primary veins going to the margin, which is serrated. Leaf unequal at

the base.]

[Illustration: FIG. 4.--Multicostate leaf of Castor-oil plant (_Ricinus

communis_). It is palmately-cleft, and exhibits seven lobes at the

margin. The petiole is inserted a little above the base, and hence the

leaf is called peltate or shield-like.]

Venation.

The arrangement of the fibro-vascular system in the lamina constitutes

the _venation_ or _nervation_. In an ordinary leaf, as that of the

elm, there is observed a large central vein running from the base to

the apex of the leaf, this is the _midrib_ (fig. 3); it gives off

veins laterally (_primary veins_). A leaf with only a single midrib is

said to be _unicostate_ and the venation is described as pinnate or

feather-veined. In some cases, as sycamore or castor oil (fig. 4), in

place of there being only a single midrib there are several large

veins (_ribs_) of nearly equal size, which diverge from the point

where the blade joins the petiole or stem, giving off lateral veins.

The leaf in this case is _multicostate_ and the venation palmate. The

primary veins give off secondary veins, and these in their turn give

off tertiary veins, and so on until a complete network of vessels is

produced, and those veins usually project on the under surface of the

leaf. To a distribution of veins such as this the name of

_reticulated_ or _netted_ venation has been applied. In the leaves of

some plants there exists a midrib with large veins running nearly

parallel to it from the base to the apex of the lamina, as in grasses

(fig. 5); or with veins diverging from the base of the lamina in more

or less parallel lines, as in fan palms (fig. 6), or with veins

coming off from it throughout its whole course, and running parallel

to each other in a straight or curved direction towards the margin of

the leaf, as in plantain and banana. In these cases the veins are

often united by cross veinlets, which do not, however, form an angular

network. Such leaves are said to be _parallel-veined_. The leaves of

Monocotyledons have generally this kind of venation, while reticulated

venation most usually occurs amongst Dicotyledons. Some plants, which

in most points of their structure are monocotyledonous, yet have

reticulated venation; as in _Smilax_ and _Dioscorea_. In vascular

acotyledonous plants there is frequently a tendency to fork exhibited

by the fibro-vascular bundles in the leaf; and when this is the case

we have _fork-veined_ leaves. This is well seen in many ferns. The

distribution of the system of vessels in the leaf is usually easily

traced, but in the case of succulent plants, as _Hoya_, agave,

stonecrop and mesembryanthemum, the veins are obscure. The function of

the veins which consist of vessels and fibres is to form a rigid

framework for the leaf and to conduct liquids.

[Illustration: FIG. 5.--Stem of a Grass (_Poa_) with leaf. The sheaths

ending in a process l, called a ligule; the blade of the leaf, f.]

[Illustration: FIG. 6.--Leaf of a Fan Palm (_Chamaerops_), showing the

veins running from the base to the margin, and not forming an angular

network.]

In all plants, except Thallophytes, leaves are present at some period of

their existence. In _Cuscuta_ (Dodder) (q.v.), however, we have an

exception. The forms assumed by leaves vary much, not only in different

plants, but in the same plant. It is only amongst the lower classes of

plants--Mosses, Characeae, &c.--that all the leaves on a plant are

similar. As we pass up the scale of plant life we find them becoming

more and more variable. The structures in ordinary language designated

as leaves are considered so _par excellence_, and they are frequently

spoken of as _foliage leaves_. In relation to their production on the

stem we may observe that when they are small they are always produced in

great number, and as they increase in size their number diminishes

correspondingly. The cellular process from the axis which develops into

a leaf is simple and undivided; it rarely remains so, but in progress of

growth becomes segmented in various ways, either longitudinally or

laterally, or in both ways. By longitudinal segmentation we have a leaf

formed consisting of sheath, stalk and blade; or one or other of these

may be absent, and thus stalked, sessile, sheathing, &c., leaves are

produced. Lateral segmentation affects the lamina, producing

indentations, lobings or fissuring of its margins. In this way two

marked forms of leaf are produced--(1) _Simple_ form, in which the

segmentation, however deeply it extends into the lamina, does not

separate portions of the lamina which become articulated with the midrib

or petiole; and (2) _Compound_ form, where portions of the lamina are

separated as detached _leaflets_, which become articulated with the

midrib or petiole. In both simple and compound leaves, according to the

amount of segmentation and the mode of development of the parenchyma and

direction of the fibro-vascular bundles, many forms are produced.

Simple leaves.

_Simple Leaves._--When the parenchyma is developed symmetrically on

each side of the midrib or stalk, the leaf is _equal_; if otherwise,

the leaf is _unequal_ or _oblique_ (fig. 3). If the margins are even

and present no divisions, the leaf is _entire_ (fig. 7); if there are

slight projections which are more or less pointed, the leaf is

_dentate_ or toothed; when the projections lie regularly over each

other, like the teeth of a saw, the leaf is _serrate_ (fig. 3); when

they are rounded the leaf is _crenate_. If the divisions extend more

deeply into the lamina than the margin, the leaf receives different

names according to the nature of the segments; thus, when the

divisions extend about half-way down (fig. 8), it is _cleft_; when the

divisions extend nearly to the base or to the midrib the leaf is

_partite_.

If these divisions take place in a simple _feather-veined_ leaf it

becomes either _pinnatifid_ (fig. 9), when the segments extend to

about the middle, or _pinnatipartite_, when the divisions extend

nearly to the midrib. These primary divisions may be again subdivided

in a similar manner, and thus a feather-veined leaf will become

_bipinnatifid_ or _bipinnatipartite_; still further subdivisions give

origin to _tripinnatifid_ and _laciniated_ leaves. The same kinds of

divisions taking place in a simple leaf with palmate or _radiating_

venation, give origin to _lobed_, _cleft_ and _partite_ forms. The

name _palmate_ or _palmatifid_ (fig. 4) is the general term applied to

leaves with radiating venation, in which there are several lobes

united by a broad expansion of parenchyma, like the palm of the hand,

as in the sycamore, castor-oil plant, &c. The divisions of leaves with

radiating venation may extend to near the base of the leaf, and the

names _bipartite_, _tripartite_, _quinquepartite_, &c., are given

according as the partitions are two, three, five or more. The term

_dissected_ is applied to leaves with radiating venation, having

numerous narrow divisions, as in _Geranium dissectum_.

[Illustration:

FIG. 7.--Ovate acute leaf of _Coriara myrtifolia_. Besides the

midrib there are two intra-marginal ribs which converge to the apex.

The leaf is therefore tricostate.

FIG. 8.--Runcinate leaf of Dandelion. It is a pinnatifid leaf, with

the divisions pointing towards the petiole and a large triangular

apex.