Page:A treatise on diamonds and precious stones including their history Natural and commercial.djvu/112

 lished projecting. The stem of the cup is now put into very powerful pincers (tongs), not unlike snuffers, which screw up with a nut and a wrench or lever, and thus hold it perfectly tight. In this position the diamond is carefully placed on the skive, the pincers resting on their legs on the bench that supports the mill, and pressing at the same time against an upright iron peg; the broad part of the tongs is next loaded with weights, to increase the pressure of the diamond upon the skive. The skive being previously set in motion, at the rate of about 200 revolutions ina minute, the process of polishing is begun. The diamond is taken up and examined from time to time, and is adjusted so as give the facet its true form. The heat occasioned by the