1854, producing, in the district including Lanark and Ayr, 717,600 tons of pig iron. Five of the 6 forges of malleable iron in Scotland are near Glasgow, and the 6 produce annually 122,400 tons. The district consumes annually 2,500,000 tons of coal. In 1854, the value of the coal and iron industries was £4,872,866, employing 38,908 persons. The St. Rollox chemical works employ 1,000 workmen in the manufacture of soda, bleaching powder, sulphuric acid, &c. There are other chemical factories in which the production of nitric and muriatic acids, chemicals of lead and iron, iodine, alum, potash, cudbear, naphtha, and bituminous oils is carried on. Since the increase of steam navigation the building of steamships and construction of engines has become a large source of industry on the Clyde. This occupation began to develop itself in 1821, and has continued to increase since.-Glasgow has but little history apart from the general history of the country. The Romans had a station on the Clyde in the locality of the city, and Antoninus's wall commenced a few miles W. of it. Local tradition assigns the foundation of Glasgow to St. Kentigern, afterward its first bishop, A.D. 539. William the Lion made it a burgh by royal charter, between the years 1175 and 1178. In 1300 a battle between the Scots under Wallace and the English under Percy was fought in the High street, when Percy was defeated and slain. In 1350, '80, and '81, Glasgow was visited by the plague. About 1542 the regent Arran besieged the earl of Lennox in the bishop's castle, obtained it upon promise of terms, and put the garrison to the sword. The same leaders soon afterward fought a battle at the Butts in the E. part of the city, where the regent gained the victory and plundered the city. In 1560 reformed superintendents superseded Catholic bishops. In 1638 the famous assembly of the Presbyterian church was held, when episcopacy was abjured. For several years thereafter the city was a prey to both parties in the civil wars. Fire, plague, plunder, and famine desolated the place. On June 4, 1690, a charter of William and Mary conferred on the townsmen the right of electing their own magistrates. Glasgow was strongly dissatisfied with the union of Scotland and England, but in 1715 and again in 1745 sided with the house of Hanover and raised a force against the Stuarts, for which the pretender's army on the retreat from Derby levied contributions and threatened to burn it. On the breaking out of the American war Glasgow raised a regiment of 1,000 men, and fitted out 14 privateers carrying 14 to 22 guns each, with an aggregate force of 1,000 men. In 1820 the public peace was disturbed by radical political, riots, and in 1848 similar demonstrations were made by the chartists.

GLASS (Sax. glas). In chemistry any product of fusion having the peculiar lustre known as vitreous, hard and brittle, whether transparent or not, is called glass. In common use the term expresses the transparent product de

rived from the fusion of silica with an alkali to which lime or a metallic oxide is added. No material invented by man is to be compared with glass in the service it has rendered. To its aid, applied in a thousand different forms, the sciences, particularly chemistry and astronomy, are essentially indebted for their advancement. It has served alike to bring within the ken of man solar systems too remote for unassisted vision to detect, and to open new worlds of living creatures too minute for their forms to imprint a sensible image upon the delicate mechanism of the eye. Thus has it extended and magnified our conceptions of the universe, and of the power of Him who created it. In every direction we find it in homelier ways applied to add to the physical comforts of man. În his habitations it is used to admit the light of day, while it serves as a screen from the wind and rain and cold. As a mirror it is made to throw back the rays that fall upon it; and perfectly reflect the images of objects, while through its transparent sheets every ray is transmitted; and in the vessels of the laboratory the processes going on in their interior are made sensible to the eye. The purity of its material causes the presence of foreign substances to be instantly detected, and it is consequently the most cleanly substance, and especially suited for vessels for holding and keeping liquids. It resists the action of nearly all the powerful chemical reagents; and but for this substance many of them would never have been known, nor could they now be made and kept.-Nothing is known with certainty respecting the early history of this invention. The fact that glass beads or other ornaments of the same material, imitating precious gems in color and beauty, have been found with mummies more than 3,000 years old, carries back the manufacture in Egypt to a very remote time. At Thebes a bead of material similar to crown glass has been found with the name of a monarch inscribed upon it who lived 1,500 years B. C.; and hieroglyphics, that must be as old as the sojourn of the Israelites in Egypt, represent glass blowers at work much after the fashion of the present day. The passage in Job xxviii. 17 is sometimes referred to as an allusion to this material, but when citing the onyx and the sapphire, the term "crystal" is very likely to have been applied to quartz or amethysts, of which cups were in those days made. In the ruins of Nineveh glass lenses, vases, bottles, &c., have been found; but there is no indication of the use of glass for windows. It is not unlikely that the substance was known long previous to the time when it was produced in beads and lenses and blown into useful shapes; for in extracting the metals of the ancient brass from their ores, and in baking bricks and articles of pottery, the workmen must often have drawn out the glassy cinders into strings, and observed the vitreous glazing produced when the clay was mixed with ashes. The lavas of

volcanoes, too, often presented to them rude forms of glass, exhibiting its plasticity, and the various colors of these artificial and natural products often no doubt suggested the possibility of imitating successfully the precious stones -those true and perfect natural glasses. From such hints the ancient Egyptians probably derived their first knowledge of glass; and profiting by them, they soon reached a high degree of excellence in the manufacture. From them the Phoenicians are supposed to have received the art, little credit being due to the tale of Pliny that it was the invention of some merchants of their nation, who observed the sand upon the beach melted by the fire and forming glass in contact with some lumps of soda. A stronger heat than could be obtained from an open fire would be required to effect this result. Nor is much more credit to be attached to his accounts respecting the production of a glass of malleable character, which when thrown upon the ground was merely indented, and could be restored to shape with a hammer, as if it were brass. Some metallic salts, as chloride of silver, possess ductility at the same time with a glassy appearance, and of one of them the articles referred to may perhaps have been made; but all modern experience is opposed to the possibility of malleability existing in a vitrified body. At Sidon and Alexandria glass works were in operation in the time of Strabo and Pliny; according to Theophrastus, the art was practised 370 years B. C., and the processes of cutting or grinding, of gilding and coloring, were then in use. Articles of exquisite workmanship were produced, but of great cost, and known only as luxuries. Vases and cups, some enamelled and beautifully cut and wrought with raised figures, and some remarkable for the brilliancy of their colors, were furnished to the Romans; and it is said that the tribute from Egypt was required by the emperor Aurelian to be paid in articles of glass. Among the most celebrated of the ancient works in glass is the Barberini or Portland vase, found in the tomb of Alexander Severus, who died A. D. 235. It is of a deep blue color, with raised figures in a delicate white enamel. The manufacture of glass was introduced into Rome in the time of Cicero; and in the 3d century articles of the material were in common use. Utensils of it have been found in Herculaneum, and in one or two instances it has been met with in windows in Pompeii. This, however, is not at the present day a very important use for glass in warm climates; and the Romans, moreover, possessed an excellent substitute for it in sheets of mica, which were in use where a protection of this sort was required. Colored window glass is known to have been used in churches in the 8th century; but for private houses glass long continued to be a rarity, and in England in the 12th century houses provided with glass windows were regarded as magnificent. In the time of the crusades the manufacture of glass was brought from

the East and established at Murano, one of the islands adjacent to Venice. Here it was long successfully prosecuted, being sustained by the fostering care of the government, and its workmen being invested with extraordinary privileges. Glass mirrors were probably first made here, and they became famous all over Europe, gradually taking the place of the mirrors of polished metal which were before in use. Many of the ornamental objects they produced were exceedingly ingenious, and are reproduced and admired even at this day. Such are the glass beads and the Venetian balls lately introduced for paper weights, made by combining together colored pieces of waste filigree glass to imitate the forms of flowers, &c., and introducing these into globes of transparent glass, which are made to collapse upon the designs by the glass blower drawing in his breath, and thus exhausting the air from the globe. The lens form of the outer covering increases the effect by magnifying the object within. The filigree work is produced by glass rods of different colors, which are melted to the outside of lumps of glass when partially shaped into decanters or other vessels. The Venetian frosted glass is an old invention, recently rediscovered by Mr. Pellatt. It is made by dipping the hot glass before blowing into cold water and instantly taking it out, softening it by heat and blowing before the cracks are melted in. The Bohemians next acquired reputation in this art; and owing to the purity of the materials found in abundance in their country, as well as to their skill, their wares still continue famous. The French, perceiving the importance of the business, early imitated the example of the Venetians, and gave extraordinary encouragement to any of the nobility who would prosecute the manufacture. In 1634 attempts were made to produce mirrors from blown glass, as was practised so successfully by the Venetians; but about the year 1666 it was found necessary to procure workmen from Venice. Works were then erected at Tourlaville near Cherbourg, which was selected from the resemblance of the locality to that of the works at Murano. In 1688 Abraham Thevart introduced in Paris the method of making large plates by casting the glass instead of blowing; he thus produced heavy plates measuring 84 inches by 50, while those previously made had barely reached in length the smaller figure named, and were necessarily thin. New works were then established at St. Gobain (in the department of Aisne); and the two companies afterward united their interests. In the 18th century the business became very successful, and has continued so to the present time, the products of the establishment ranking among the first in quality in the world.-The manufacture of window glass, according to an old builder's contract, brought to light by Horace Walpole, and copied into his "Anecdotes of Painting," was conducted in England as early as the year 1439; but a decided preference was given to that "from beyond the seas." It was

commenced in London in 1557; and soon afterward flint glass also was made there. The production of plate glass was undertaken in 1670 at Lambeth by the duke of Buckingham, who imported Venetian workmen. The government encouraged the enterprise by a bounty upon the glass intended for exportation; and under this protection, also extended to the different branches of the manufacture, by which the cost was reduced from 25 to 50 per cent., many other glass factories sprung up in different parts of the kingdom; but their prosperity and the progress of the art were afterward greatly checked by the excise duties imposed, and the surveillance of crown officers over all the operations of the works. The bounties and the duties, with their annoying restrictions, were annulled in 1845, when the suddenly increased demand for home consumption brought into existence many more establishments. In 1847 there were in all 24 window glass factories in Great Britain. In 1858 the number was reduced to 8. The capacity of their production is, however, immense, as is shown by the fact that the firm of Chance and co. executed the large order in sheet glass for the crystal palace in 1851 without materially affecting their ability to fill their general orders. The British exports of glass in 1844 amounted to £26,694 in value; in 1855 they exceeded £500,000. The quality of their crown glass is unrivalled.-Belgium is said to be the greatest glass-producing country in the world. In 1854, as stated by Mr. Hartley of Sunderland, the annual production of sheet glass had amounted to 50,000,000 square feet, or 22,300 tons, which was one fourth more than was made in England of both crown and sheet glass. Of this, 85 per cent. was exported, 6 per cent. being sent to England. Of the English production, 85 per cent. was at that time retained for home consumption. -Glass appears to have been one of the earliest branches of manufacture introduced into the United States; but to what extent it was carried on in early times is unknown. In Salmon's "Modern History" (London, 1746), vol. iii., p. 440, mention is made of glass works which were commenced at Jamestown, Va., and the completion of which was interrupted by the Indian massacre of March 22, 1622; and in Howe's "Historical Collections of Virginia," p. 39, is a quotation from "Smith, book iv. p. 18," in which, under date of 1615, it is said that "for a long time the labor of the colony had been misdirected in the manufacture of ashes, soap, glass, and tar, in which they could by no means compete with Sweden and Russia." But the first glass factory in the United States of which we have a precise account was built by Mr. Robert Hewes of Boston, Mass., in the town of Temple, N. H., in 1780. From information obtained by Mr. H. A. Blood, the historian of that town, it appears that the works were located there on account of the cheapness of fuel and labor. The building, of which the ruins are still to be seen, was 65 feet square, and the glass blowers, 32 in number, were German (Hessians and Wal

deckers) deserters from the British army. In the winter of 1780-'81, in consequence of the carelessness of a drunken furnaceman, the works took fire and were destroyed. Some of the manufactured articles, of a greenish color, are still preserved. A large circular plate, the product of the first operations, was presented by Mr. Hewes to Harvard university. To encourage the rebuilding of the works, the state of New Hampshire, on the petition of Mr. Hewes, authorized him, by act of the general court of March 30, 1781, to issue lottery tickets, and by their sale raise the required capital. The attempt, however, was not successful. From an allusion to this subject by Washington in his diary (1789) it would appear that glass was made at that time in New Haven. In 1800 an unsuccessful attempt was made to establish the business in Boston. In 1803.a German named Lint took charge of the Boston works, and the state of Massachusetts agreed to pay the proprietor a bounty on every table of window glass made. Since that time the works have prospered, and many new enterprises have been started, but the greater number of these have been abandoned. The most important flint glass works now in operation are 3 factories in S. Boston, 2 in E. Cambridge, and one at Sandwich, Mass., 2 in Brooklyn, N. Y. (one of plate glass commenced in 1855, but now discontinued), one in Jersey City, and 2 in Philadelphia. In the southern part of New Jersey are the most extensive works producing window glass, and about Pittsburg, Penn., and the river towns below, and also in central New York, the manufacture is carried on in numerous factories. The first plate glass manufactory was established at Cheshire, Berkshire co., Mass., about 1853. The company afterward removed its works to Lenox, in the same county, and is known as the "Lenox Rough Plate Glass Co." It is the only establishment now in operation devoted to this branch. Henry R. Schoolcraft was engaged in his youth in the manufacture of glass at Cheshire, and in 1817 published a treatise entitled "Vitreology," designed to exhibit the application of chemistry to this art.-Glass is a chemical compound of variable ingredients, different substances of similar character replacing each other to produce its varieties. Silicic acid or silica is its principal element, which combines with the potash, soda, oxide of lead, lime, alumina, and other substances that may be added, to produce silicates of these bases. By the manufacturer the bases are classed as fluxes. Boracic acid may take the place of silicic acid to produce vitreous borates or glass. The proportions of the bases named admitting in their use of indefinite variations, a wide scope is given for the exercise of the skill of the manufacturer in producing any particular quality of glass. The metallic oxides also afford him abundant resources for imparting any desired hue to his product, according as these are judiciously selected and introduced. The important requisite in all the varieties of glass is a fusible compound, which solidifies on

colors. 7. Enamel, composed of silica, soda, and oxide of lead, but rendered opaque by oxide of tin or antimony, which form a stannate or antimoniate with the soda. To these may be added the soluble glass, which is a simple silicate of soda or of potash, or a mixture of the two silicates. The chemical formula of bottle glass No. 4 (see table on preceding page) is KO+8CaO+2A1, O3+F2 O3+8SiO3; of window glass No. 1, 3NaO+5CaO+12SiO,; of plate glass No. 1, 2NaO+CaO+6SiO; of white glass No. 3, KO+CaO+3SiO,; of flint glass No. 2, 6KO+9PbO+20SiO.; of strass (flint glass No. 3), 3KO+9PbO4 16SiO.. The last variety, well known to chemists, is of variable composition, some qualities melting readily. To the later editions of Dr. Knapp's work are added the following more recent analyses by Peligot:

The second of these is a remarkable glass, being a simple silicate of potash with 10 per cent. more silica than is contained in Fuchs's soluble glass (a notice of which is introduced near the close of this article). Particles of glass are dispersed through the semi-transparent, imperfectly melted mass. The compound is not at tacked by boiling water, and does not attract moisture from the air. The ingredients of glass appear to be in the proportions of chemical equivalents-results, however, obtained by practice and not by mixtures made with this view. Various causes affect the stability of the combinations and the qualities of the compounds. The alkali in window glass powdered and moistened is detected by its action upon turmeric paper, and may be partially dissolved out by long continued digestion in boiling water. Atmospheric agents sometimes remove it in part from window panes, leaving a film of silica or silicate of lime. The glass of stable windows is liable to change its appearance, and assume prismatic colors, from the action of the ammoniacal vapors upon the silica. Changes in the degree of oxidation of its metallic ingredients, which are sometimes induced by atmospheric causes, are also attended by changes of colors. Long continued cooling has the effect of changing the structure, causing it to lose its transparency and become devitrified. Its ingredients form among themselves a new arrangement of their particles, and compounds are produced which assume a crystallized structure. By remelting, the vitreous character: may be restored, though with a loss of a portion of potash which was volatilized in the devitrification. In making articles of glass, and especially bottles, it is necessary to guard against this tendency to crystallize, and shorten the process of annealing on account of it. Devitrified glass was first

described by Réaumur, and has hence been called Réaumur's porcelain. In consequence of the ease with which it may be made into any shape, and its tenacity and refractory nature, not unlike porcelain itself, it has been thought that it may be employed as a cheap substitute for this material, especially in many articles used in chemical laboratories.-The specific gravity of glass varies with its composition, from 2.4 to about 3.6. The determination of this may afford some hints as to the composition of crystal or flint glass, but is no index to that of the other varieties. Its density and also its refractive property are increased with the proportion of oxide of lead it contains. Brittleness is a quality that limits the alteration of the shape of glass within narrow bounds, after it has cooled; but when softened by heat while it is highly tenacious, no substance is more easily moulded into any form, and it can be blown by the breath into hollow vessels of which the substance is so thin that they may almost float in the air. It may also be rapidly drawn out into threads of several hundred feet in length; and these have been interwoven in fabrics of silk, producing a beautiful effect. In the soft plastic state it may be cut with knives and scissors like sheets of caoutchouc. It is then inelastic like wax; but when cooled, its fibres on being beaten fly back with a spring, and hollow balls of the material have, when dropped upon the smooth face of an anvil from the height of 10 or 12 feet, been found to rebound without fracture to or the same height. It has the valuable property of welding perfectly when red hot, and portions brought together are instantly united. When moderately heated it is readily broken in any direction by the sudden contraction caused by the application of a cold body to its surface. It is also divided when cold by breaking it along lines, cut to a slight depth by a diamond, or some other extremely hard-pointed body of the exact form suited for this purpose; and it may be bored with steel drills, provided these are kept slightly moistened with water, which forms a paste with the powder produced. Oil of turpentine, either alone or holding some camphor in solution, is also used for the same purpose. Copper tubes fed with emery also serve to bore holes in glass. Acids and alkalies act upon glass differently according to its composition, and reference should be made to this in storing different liquids in bottles. Silicate of alumina is readily attacked by acids, and bottles in which this is in excess are soon corroded even by the bitartrate of potash in wine, and by the reaction the liquor itself is contaminated. A glass that loses its polish by heat is sure to be attacked by acids. Oxide of lead when used in large proportion is liable to be in part reduced to a metallic state by different chemical reagents, and give a black color to the glass. All glasses are attacked by hydrofluoric acid.-The crude materials employed in the manufacture of glass are selected with more or less care according to the quality of the