Page:Popular Science Monthly Volume 88.djvu/770

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��Popular Science Monthly

��Why Can't We Make Diamonds

WE can. But they are so small that a microscope has to be used to see them. There is no chemical differ- ence between the graphite in your pencil, the coal in the kitchen stove and the dia- mond. All are forms of carbon, and the diamond is but crystallized carbon. The Kohinoor that blazes in the diadem of a potentate was crystallized by nature from something like coal.

Molten iron will dissolve carbon, just as sugar is dissolved in water. Like water it chills and solidifies when it ex- pands. A French physicist, Moissan, heated a crucible containing a mixture of pure iron and carbon to a tempera- ture of seven thousand degrees Fahr. He dropped the white-hot crucible into cold water. The resulting contraction pro- duced great pressure, and in that press- ure diamonds w^ere formed, not Kohi- noors, but microscopic crystals, each of which cost about five times as much as a natural diamond of equal size. Sir William Crookes, the distinguished Eng- lish chemist, obtained minute diamonds also by combining great heat with great pressure. He exploded cordite, to which carbon had been added, in a closed cham- ber. In other words he used a kind of cannon the mouth of which had been sealed. If w^e are to make big, salable diamonds we must have far more power- ful mechanism at our disposal. Some day that mechanism will be provided, and the diamond factory of Niagara Falls will compete with the Kimberley Mines of South Africa.

A Lace Curtain Protection

IN the summer, when the windows are opened, the housewife may be an- noyed by the fact that the lace curtains blow against the screens, and become rusty and dirty. This can be avoided by placing a small tack at each side of the window and tying a piece of white cord from one tack, across to the other. This will keep the curtains clean.

When a person sits near the window he may be bothered by the curtain blow- ing against him. Now, if another piece of string is placed exactly where the first piece was, and the curtain is placed be- tween the two, it will be kept there ; and both difficulties will be solved.

��Eliminating Pottery Waste

POTTERY-MAKING has been, until recently, one of the few remaining industries where the skilled workman held absolute sway. And even with the most skilled of firemen, the variation in the degree of heat in the kilns was still so great that the loss in ruined pottery and "seconds" was immensely high.

Not long ago an Englishman, Conrad Dressier, invented, for use in the glazing of wall tiles, a tunnel-kiln in which small carloads of material could be fired at once, and in which, by means of the generation of the heat from gas-pro- ducers, a saving in fuel up to eighty per cent could be affected. Not only this, but the temperature was kept so even that the wastage from ruined tiles and "seconds" was eliminated almost en- tirely, and the whole device could be con- trolled by unskilled workmen.

The oven has recently been applied to the kindred art of pottery-making, and in several large plants has taken the place of the old ovens, with vast saving to the company, though perhaps deliver- ing a blow to that notable American in- dustry, the five-and-ten-cent-store, where "seconds" delight the economical.

In pottery the clay bodies are changed in chemical and physical structure at a temperature varying from two thousand to twenty-five hundred degrees Fahren- heit, and to fall short of this tempera- ture or to increase it unduly for any length of time, is to spoil the merchandise.

The gas from the producer enters the tunnel-kiln and is burnt, not among the wares to be baked, but in two long tubes running lengthwise of the tunnel, from which the fumes are carried off outside the kiln. The control of gas and air for its combustion is regulated auto- matically or at will, and is thoroughly even. The goods to be fired are put on the trucks, and propelled by a small mo- tor, taking about one hour for the trip, not including the cooling in a heated chamber.

This kiln was first used in this country by a manufacturer of sanitary porcelain ware, and the scene reproduced here is from this American plant. The goods, in all cases, are placed on the shelves of trucks, which commence at two feet from the ground and rise to five feet for their trip through the long kiln.

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