made elsewhere, aftd for many years commanded themarket of nearly all Europe . Their most extensiveglass-works were established at Murano, a small vil-lage in the vicinity of Yenice; but the produce wasalways recognised as Venetian glass.
The skill of the Venetians in glass-making wasespecially remarkable in the excellence of their mirrors.Beckmann, who has minutely investigated the subject,is of opinion that the manufacture of glass mirrorscertainly was attempted, but not with complete suc-cess, in Sidon, at a very early period ; but that theyfell into disuse, and were almost forgotten until thethirteenth century. Previously to this period platesof polished metal were used at the toilette ; and inthe rudeness of the first ideas which suggested thesubstitution of glass, the plates were made of a deepblack colour to imitate them. Black foil even waslaid behind them to increase their opacity. Themetal mirrors, however, remained in use long afterthe introduction of their fragile rivals; but at lengththey wholly disappeared, a result effected chiefly bythe skill of the Venetians , who by silvering the glassgreatly improved the manufacture.
From Italy the art of glass-making found its wayinto France , where an attempt was made to rival theVenetians in the manufacture of mirrors. The firstessay was unsuccessful; but another, made under thepatronage of Colbert, had better fortune. A fewyears afterwards, a discovery or rather improvementin the art of glass-making was effected by AbrahamThevart. This improvement consisted in castingplates of much larger dimensions than it had hithertobeen deemed possible to do. Tiievart’s first plateswere cast at Paris, and astonished every artist bytheir magnitude. They were 84 inches long and 50inches wide, whereas none previously made exceeded45 or 50 inches in length.
Early in the fourteenth century the French govern-ment made a concession in favour of glass-making,by decreeing, that not only should no derogationfrom nobility follow the practice of the art, but thatnone, save gentlemen or the sons of noblemen,should venture to engage in any of its branches, evenas working artisans.
The first mention of English window glass is in acontract dated 1489, between the Countess of War-wick and John Prddde of Westminster, glazier,whom she employed to embellish a tomb for the earl,her husband. John Prddde is thereby bound to useno glass of England, but glass from beyond seas. Thefinest sort of window-glass was first made at CrutchedFriars, London , in 1557. The first flint-glass madein England was manufactured at the Savoy House,in the Strand; and the first plate-glass, for looking-glasses, coach windows, and similar purposes, wasmanufactured at Lambeth by Venetian workmen,brought over in 1670 by the Duke of Buckingham.From that period the English glass manufactories,aided by the liberal bounties granted them in cashupon glass sold for export, became powerful andsuccessful rivals of the Venetian and French manu-factories. The bounty on glass exported, whichthe government paid to the manufacturer, was not
derived from any tax by impost or excise previouslylaid on the raw materials ; for all such were returnedto the manufacturer, together with the bounty,thereby lessening the actual cost of the article from25 to 50 per cent., and enabling the English exporterto compete successfully in foreign markets. Thisbounty provision was annulled during the premier-ship of Sir Robert Peel , together with all the exciseduty on home consumption.
The art of glass-making was introduced into Scot-land in the reign of James VI . An exclusive rightto manufacture it within the kingdom, for the spaceof thirty-one years, was granted to Lord GeorgeHay in the year 1618. This right his lordshiptransferred in 1627, for a considerable sum, toThomas Robinson, merchant-tailor in London , whoagain disposed of it for £260 to Sir Robert Mansell,vice-admiral of England. The first manufactory ofglass in Scotland , an extremely rude one, was estab-lished at Wemyss, in Fife . Regular works wereafterwards commenced at Prestonpans, Leith, andDumbarton.
Composition of Glass. —This substance is the pro-duct of fusion at a high temperature of the metals ofthe alkalies and alkaline earths, or silicic acid, some-times of boracic acid, with lead, tin, iron, manganese,&c. The product solidifies after fusion in the formof a transparent mass, which is either colourless ornot, according to the ingredients which it contains;it combines a great degree of hardness with theproperty of resisting the destructive action of air,water to a certain extent, and even that of the morepowerful chemical agents. It is well known thatsilica acts the part of a powerful acid at the tempera-ture of a red heat, and is capable of expelling car-bonic acid, hydrochloric acid, &c.
Those varieties of glass which possess the highestdegree of lustre and power of refraction are also thesoftest, that is, the most easily scratched. They arelikewise those which exhibit the highest specificgravity (from 2-8 to 8‘6) and, as might be deducedfrom that circumstance, they (at least as far as thecolourless glasses are concerned) are those whichcontain bases with a very high atomic weight—oxideof lead, baryta. Those bases, on the contrary, whichrender the glass hard and durable, appear to producelittle lustre or power of refraction. The specificgravity of these varieties lies between 2-37 and 2'56.
There is much difficulty in dividing the glassesaccording to any definite principle. One of thesimplest arrangements is given by Tomlinson, asfollows:—
1. Silicate of potash and oxide of lead. Examples;— Flint-glass, crystal, and strass.
2. Silicate of soda and lime ; or silicate of potash,soda, and lime. Examples :— Common window , Eng-lish crown, and plate.
8. Silicate of potash and lime. Examples:— Foreigncrown, refractory Bohemian glass.
4. Silicate of soda, lime, alumina, and oxide of iron.Example :— Coarse green wine-bottle glass.
Bottle-glass, or what is more properly describedby the German term Ilohlglase, or Hollow glass, com-