SCIENCE, INVENTION, DISCOVERY. 



307 



superfluous color from its surface, so that only 

 the design cut in the metal is imprinted in 

 clear outline upon the cloth. The employ- 

 ment of a number of rollers to make one design 

 is attended with much difficulty, as in passing 

 under them the cloth is in much danger of 

 being displaced and the regularity of the print 

 destroyed. As the cloth leaves the printing- 

 machine it is drawn over rollers through a 

 hot-air chamber, by which it is thoroughly 

 dried, and the colors become fully set. 



Candles. It was not until the fourteenth 

 century that candles having any resemblance 

 to those now in use were manufactured. Pre- 

 vious to that time our English ancestors soaked 

 splints of wood in fat or oil to obtain their 

 light. The candles used by the Greeks and 

 Romans were rude torches made by dipping 

 strips of papyrus or rushes into pitch and then 

 coating them with wax. These candles were 

 also in use in Europe during the middle ages, 

 and were very large and heavy. A dipped 

 candle made from tallow was introduced in 

 England in the fourteenth century, and wax- 

 candles were also made at the same time. 

 These latter were very costly, and were con- 

 sidered great luxuries. In 1484 a company 

 for the manufacture of wax candles was incor- 

 porated in London. Mold candles are said to 

 be the invention of the Sieur Le Brez, of Paris. 



Casting Plate-Glass. The whole oper- 

 ation of casting a plate of glass occupies but a 

 very short time. The casting-tables, the most 

 important pieces of apparatus in plate-glass 

 works, are 19 feet long, 14 feet wide, and 7 

 inches thick. Each is provided with an iron 

 roller 30 inches in diameter and 15 feet long. 

 Strips of iron on each side of the table afford 

 a bearing for the rollers and determine the 

 thickness of the plate of glass to be cast. The 

 rough plate is commonly 9-16ths of an inch in 

 thickness. After polishing, it is reduced to 

 6-16ths or 7-16ths. The casting- tables are 

 mounted 'on wheels, and run on a track that 

 reaches every furnace and annealing-oven in 

 the building. The table having been wheeled 

 as near as possible to the melting-furnace, the 

 pot of molten glass is lifted by means of a 

 crane and its contents quickly poured on the 

 table. The heavy iron roller is then passed 

 from end to end, spreading the glass into a 

 layer of uniform thickness. The cold metal 

 of the table cools the glass rapidly. As soon 

 as possible the door of the annealing-oven is 

 epened and the plate of glass introduced. The 

 floor of the oven is on the same level as the 

 casting-table so the transfer can be conve- 

 niently and quickly made. When, after sev- 

 eral days, the glass is taken out of the oven, 

 its surface is found to be decidedly rough and 



uneven. A small quantity is used in this con- 

 dition for skylights and other purposes where 

 strength is required without transparency. It 

 is known as rough-plate. The greater part of 

 the glass, however, is ground, smoothed, and 

 polished before it leaves the establishment. 

 Few industries offer such fine scenic displays 

 as the pouring of the molten glass. 



Celluloid is made from the cellulose con- 

 tained in cotton cloth or raw cotton . The cot- 

 ton is treated to a weak solution of nitric acid. 

 This has the effect of making a, pulp of cotton 

 very much like paper pulp. After the acid 

 has acted the pulp is treated to a copious water- 

 bath that in a large measure washes out the 

 acid. Then it goes through a partial drying 

 process, and a large quantity of camphor-gum 

 is mixed with it, and it is rolled into sheets 

 ready for the drying-room, where it is dried on 

 hot cylinders, the same as paper is dried. It 

 can be softened by steam, but hardens again 

 when it is dry. Celluloid, when ready for 

 market, burns as readily as ordinary sealing- 

 wax. 



Chess, Origin of. Although the origin 

 of chess is enshrouded in considerable mystery, 

 there is but little doubt that its birthplace 

 was in India, and that it is an offspring of a 

 game called Chaturanga, which is mentioned 

 in Oriental literature as in use fully 2,000 

 years before the Christian era. From India 

 chess spread into Persia, and thence into Ara- 

 bia, and ultimately the Arabs took it to Spain 

 and the rest of Western Europe. The game 

 was in all probability invented for the purpose 

 of illustrating the art of war. The Arab legend 

 upon this point is that it was devised for the 

 instruction of a young despot by his father, a 

 learned Brahman, to teach him that a king, 

 notwithstanding his power, was dependent for 

 safety upon his subjects. The Greek histo- 

 rians credit the invention of the game to Pala- 

 medes, who, they claim, devised it to beguile 

 the tedium of the siege of Troy during the 

 Trojan war. 



Common Names of Chemical Sub- 

 stances. 



Aqua Fortis, 



Aqua Regia, 



Blue Vitriol, 



Cream of Tartar, 



Calomel, 



Chalk, 



Salt of Tartar, 



Caustic Potassa, 



Chloroform, 



Common Salt, 



Copperas, or Green Vitriol, 



Corrosive Sublimate, 



Diamond, 



Dry Alum, 



Epsom Salts, 

 Ethiops Mineral, 

 Galena, 



Nitric Acid. 

 Nitro-Muriatic Acid. 

 Sulphate of Copper. 

 Bitartrate Potassium. 

 Chloride of Mercury. 

 Carbonate Calcium* 

 Carbonate of Potassium. 

 Hydrate Potassium. 

 Chloride of Gormylc. 

 Chloride of Sodium. 

 Sulphate of Iron. 

 Bi-Chloride of Mercury. 

 Pure Carbon. 

 Sulphate Aluminium and 



Potassium. 



Sulphate of Magnesia. 

 Black Sulphide of Mercury. 

 Sulphide of Lead. 



