192 ANNUAL OF SCIENTIFIC DISCOVERY. 



ON THE MANUFACTURE OF SMALT. 



THIS branch of manufacture is altogether foreign ; and the chief ma- 

 terial for it is almost entirely obtained from two small districts, one in 

 Saxony, on the borders of Bohemia, and the other in Norway. The uso 

 of the ore from which smalt is manufactured, was discovered by one 

 Schurer, a glass-maker, at Neudeck. He first collected some of this 

 ore and tried it in his glass furnace, when he found, to his delight, that 

 it communicated to glass a beautiful blue color. This was about the 

 year 1540. Schurer made many trials of the new material, and at 

 length succeeded in making of this blue glass an enamel color, well 

 adapted to the use of the potter. This color found its way to Nurem- 

 berg, and at length to Holland, where it was highly appreciated by the 

 Dutch artists. They sought out the humble glass-maker of Neudeck, 

 and invited him, by large promises, to reveal his secret. He took up 

 his residence, for a time, in Magdeburg, and had the ores conveyed 

 thither for the purpose of his manufacture. But he afterwards returned 

 to Neudeck, and constructed a mill for grinding the glass to powder. 

 Meanwhile the Dutch became so expert in the preparation of the color, 

 that the Elector of Saxony had to invite the color-makers of Holland to 

 teach their methods to his people ; after which, color mills rapidly in- 

 creased in the neighborhood of the cobalt mines. Thus for a very 

 long period this beautiful color continued to be manufactured from a 

 mineral whose composition was unknown. It was not till the year 

 1733, that the Swedish chemist, Brandt, obtained from this ore the 

 metal which he called cobalt, and proved that the coloring matter is the 

 protoxide. 



Metallic cobalt is a brittle metal, of a reddish gray color ; it fuses 

 with difficulty, and has a magnetic character. This metal has not been 

 applied to any useful purpose in the arts, and the interest attaching to 

 it is purely scientific. To obtain the oxide in a state of tolerable pu- 

 rity, requires much careful and laborious manipulation, varying some- 

 what according to the nature of the ore. The first process is picking, 

 by which stony fragments are removed, and the ores are separated into 

 different qualities, the richest being set aside for roasting with little or 

 no previous preparation, and those containing nickel being reserved for 

 special treatment. The larger bulk of the picked ore is, however, sub- 

 jected to the next process, which is stamping in a stamp-mill. The 

 stamp-troughs are furnished with a stream of water, which washes out 

 the pounded ore and carries it down an inclined plane, where the sand 

 and earthy matters, being much lighter than the metallic oxides, are 

 carried farthest by the action of the stream, and are easily separated 

 from the heavy and valuable particles. The ore thus washed is next 

 roasted in a reverberatory furnace, provided with chambers for receiv- 

 ing and condensing the arsenic. The condensing tube is connected 

 with chambers of several stories, where the arsenic is collected by men 

 wearing a dress fitting tightly in every part, a helmet with goggles for 

 the eyes, and a wet bandage or sponge tied over the mouth and nostrils. 

 They are still further fortified for their dangerous occupation by drink- 

 ing a glass or two of olive oil. Their food, also, is regulated, and con- 

 sists chiefly of vegetables with abundance of butter. In the roasting 



