742 



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. 



