THE INDUSTRY OF ALL NATIONS.

as Drayton’s process. The silvering fluid is composed of one ounce of nitrateof silver, three ounces of alcohol of 87 per cent., and 20 or 30 drops of oilof cassia. Metallic silver is deposited from this fluid upon the addition of areducing liquid composed of one part of oil of cloves dipped in three parts ofalcohol. The silver begins immediately to be thrown down, but the experimentsucceeds best when the process goes on slowly, and from the addition of a fewdrops (say six or eight drops) of the reducing fluid, which suffice to precipitatethe silver of 4J oz. of solution. The film of silver does not exceed 15 or 20grains in weight for a foot of surface. Flat mirrors can be thus silvered as wellas globular vessels, and the cost of silver upon a mirror 5 feet by 10 would notexceed two and a half dollars. There are, however, it is said, practical difficultiesin the ways of employing this process on a large scale, but for the silvering ofthe interior of glass vessels it is invaluable. The precipitation of the silver inthis process is due to the deoxydizing influence of the volatile oil, and many otherorganic compounds possess the same power over the oxyd of silver.

Bottle Glass is extremely various in its composition, since these vessels may beblown from any description of metal. For wine bottles cheapness and strengthare the great requisites, and as color is of no moment in this case, materials whollyunfit for other uses may be employed. Thus black bottles are made of 100 partsof sand, 20 lbs. dry glauber’s salts (sulphate of soda), 18 soap boiler’s waste, 200 ofrefuse glass, and 45 of basalt. For ordinary green glass bottles, 100 parts sand,72 of lime, and 280 of lixiviated wood ashes. Champagne bottles require 100 partssand, 200 feldspar, 20 lime, 15 common salt, and 125 slag from the iron furnace.*White bottles for medical and chemical use are blown from any good quality of hardglass, but those for chemical use should contain neither lead nor arsenic, and nomore alkali than is requisite for fusion. Insolubility and power to resist chemi-cal action, are indispensable qualities in chemical vessels. No glass is absolutelyinsoluble, as even the hardest Bohemian white glass (a lime-potash glass), whenpulverized and moistened with water always yields an alkaline reaction to testpapers. Tubes of glass for chemical use when intended to resist a high tempera-ture, as in organic analysis, are formed of the most refractory metal, such as hasbeen made in perfection only in Bohemia and some other Austrian provinces.This glass is composed of silica 73, potash 113, soda 3, lime 105, alumina, &c.,2=100. The usual glass for chemical use is formed from 100 lbs. white sand,41.4 potashes, and 17.5 of lime. Glass of this composition is not easily fused, andis more difficult to work than that which contains more alkali. In comparingthe composition of the coarser sorts of bottle glass, one is struck with the resem-blance, between them and some other natural products, like obsidian and lava,which are fusible silicates of alumina and iron, with variable proportions oflime, magnesia, and the alkalies. We may in fact regard these volcanic productsas nature’s glass*

Flint Glass or Crystal .—Some confusion exists in the use of these terms, ow-ing to the fact that flint glass is a term usually restricted to that description ofglass of which oxyd of lead forms an important constituent. This is not,however, strictly true, as the Bohemian flint glass contains no lead at all. Wemay define flint or crystal glass to be that description of glass which is fittedfrom its comparative softness for easy grinding or cutting on the polishingwheel, and which also has a high refracting power, and is thereby best adaptedfor articles of beauty and luxury', in which brilliancy of lustre is desired. Itwas remarked at the opening of this essay that the oxyd of lead had a most re-markable power of dissolving silica, and that the glass formed by it was distin-guished by its brilliancy, easy fusibility, and weight. The use of oxyd of lead inthis art was first resorted to in England in the 16th century, as an expedient toprocure a more easily fusible glass, in order to avoid the waste of fuel required toheat close or arched pots to the proper temperature by means of coal, the onlyfuel available in England, and one incompatible with the use of open pots. It wassoon discovered that the lead was not only an excellent flux, but that the glassmade by it had superior beauty from its high refracting powers. Subsequently theuse of lead was adopted in France, but in Bohemia and Venice they still makecrystal glass without its use.

The Bohemian crystal for grindingis composed of 100 parts white sand, 60 purepotashes, 8 chalk, 40 broken glass, and If manganese. The English flint glass iscomposed of sand, minium, and potashes, all pure as possible in the proportionsof about 3,2,1. In addition manganese or arsenic is used as a decolorizing material;if the former is selected, care is taken that it is pure, and especially that it is freefrom iron. Minium, or red lead, (Pb 0 2 ) in the process of fusion parts with oneatom of oxygen to form that oxyd (Pb O), which unites with the silica, and thisliberated oxygen acts to decolorize the glass. With the same object a part of thecarbonate of potash may be advantageously replaced by its equivalent of nitrateof potash (saltpetre), which acts favorably by the large volume of oxygen it parts

* We may mention here the specimens of “ Lava Ware,” manufactured from the slags of iron reduc-ing furnaces, exhibited by Dr. Wm. A. Smith, of Philadelphia, Penn., (U. S. Class 27, No. 19). Dr.Smith claims that he has found important uses for the slags of the iron furnaces which have here,tofore been waste products. He exhibits black bottles, tiles and square slabs moulded from this material,which., as we understand, is subject to a second fusion, although it is perhaps possible to work it from theoriginal heat of the furnace.

^ 154

With wood as fuel.100 lbs.

45 “

35 “

with at a high temperature. More silica can be used with wood fuel than withcoal. Thus the composition of flint glass is stated :

With coal as fuel.

Sand washed and calcined, 100 lbs.

Minium (oxyd lead), 70 “

Purified Potashes, 30 “

Cullet, or broken glass.

The fusion of these materials occupies six or eight hours, and the fining asmuch more, during which the glass must be protected from the smoke and pro-ducts of combustion, the action of which would reduce the oxyd of lead to me-tallic lead, and so blacken the product. Eight crucibles or pots are usually set inone large circular furnace all heated by one fire, which is conducted by the flues soas to surround the pots on all sides. In England and the United States it is usualto commence th 6 found or fusion of the materials on Friday night, and to leave themetal until Monday morning before commencing work, during which time it be-comes perfectly fined. It is in this department of glass manufacture that moreprogress has been made than in any other in the United States, and the best resultsobtained. The Brooklyn Flint Glass Co. (Class 24, No. 1, U. S.), and the NewEngland Glass Co., Boston (Class 24, No. 4, U. S.), are the largest manufacturers,and their display in the present Exhibition of dioptric lenses, and signal lamps,and of plain, pressed, cut, and decorated glassware, is decidedly creditable to thiscountry. The American flint glass is distinguished by its brilliancy and the purityof its color, and that of the New England Co., is the best pressed glass probablyever manufactured. The composition of the New England Glass Company’swares is as follows:

Best colorless sand, - - - 300

Minium, .... 200

Refined Pearlash, ... looCullet and manganese, or arsenic.

When requisite, a part of the pearlash is replaced by nitre. The art of mould-ing or pressing glass in metallic moulds as a substitute for blowing and cutting, it isbelieved, is entirely of American origin, and although adopted to some extent inEurope, the products there are very inferior in beauty. Indeed the process of mould-ing glass, so far as we can learn, is used in Europe only as a preparation for cutting,the labor of which process is thereby very much reduced. But the New EnglandCompany have brought the process to so much perfection, that their drinking ves-sels are made by it of such finish and beauty as to deceive the eye, except on closeinspection, with the idea that they are cut. We have taken some pains to ascer-tain the history of this branch of glass making in the United States, and have beenobligingly furnished with some facts relating to it by Mr. Jos. N. Howe, the Agentof the New England Company. It appears that moulded glass has been made fora long time in a certain rude form, but that in 1826 Mr. Enoch Robinson, then inthe employ of the New England Company, took out letters patent for the inventionof a process by which furniture knobs, door handles, &c., were made of pressedglass. The validity and originality of this patent was fully tested by a closelyconteste d lawsuit in Philadelphia, carried on against powerful parties in Pittsburgh.In 1827 Mr. Robinson, against the ridicule of the craft, succeeded in moulding a saltstand, and various other articles for table use, and from that time the invention, asone of general applicability, may be considered as established. In 1832 about£100 sterling in value of the Boston pressed ware was taken to London by Mr.Ryan, an Englishman, where the articles in question excited much curiosity andsold profitably. But it was only so late as 1837 that a thin vessel like a drinkingglass was fashioned by the pressing process, which branch of the manufacturehas since steadily increased. The show of pressed articles in flint glass bythe New England Company in the present Exhibition is particularly creditableto the high reputation of that establishment, and the more so, that, as we areassured by the agent, the articles shown were not made for this occasion, butwere selected from saleable goods on the shelves of the warehouse. Mr. Howestates that the art of pressing glass, as now carried on in the United States, hasworked an entire revolution in the business of flint glass manufacture with us,from the increased facility it affords in making the great variety of articles'andpatterns susceptible of being thus produced, while the diminished cost of produc-tion therefrom resulting, has wonderfully increased the competition among rival

companies.

From flint glass are formed all the numberless and nameless articles of glass,which are employed as objects of utility or ornament for the table, the toilet, theparlor, or the cabinets of the curious. To attempt the most summary sketch ofthe numerous processes by which these objects are produced and ornamented, wouldbe hopeless in any reasonable space. A glance at the Austrian and FrenchCourts in the present Exhibition will convey an idea of what modern art has ac-complished in this department of manufacture. Our illustrated pages have alsobeen enriched by designs copied from many, of these objects.

We trace to Venice the origin of all ornamental and colored glass blowing,and the processes still in use at Murano are believed to be the same which havebeen practised there for centuries past. Among the objects thus made whichmost excite the wonder of those uninformed in the steps of the process, are the