THE ART OF THE CUTTER
	far too great for an ordinary cement, no matter how hard, to be used to fix the stone to the dop. So a solder or fusible alloy, composed of tin and lead, is substituted. The dop con­taining the solder usually has an external diameter of 1-1/2 inches, and a stout copper stalk is fixed to the bottom of the dop. The dop is placed in a nonluminous gas flame and heated until the solder softens, when it is removed by means of the small tongs and placed upright on a stand. Long tongs are used for shaping the solder into a cone, at the apex of which the diamond is placed. The solder is worked well over the stone, so that only the part to be polished is exposed. While still hot, the dop, with the stone in position on the solder, is plunged into water in order to cool it. The fact that diamonds withstand this drastic treatment testifies to their thermal conductivity. Any other gem in the circumstances would split into pieces. The dop is now ready to be attached to an arm or tongue; kits copper stalk is placed in the groove that runs across the split end of a screw, worked by a nut. Four arms, each carrying a dop, can be used with one polishing wheel. The copper stalk we were talking about is important. It is strong yet flexible, and thus can be bent so as to place the diamond in the position corresponding to the facet required to be polished. When the workman receives the rounded stone he first must ascertain its point and therefore the direction of the grain. Remember we already discussed that technical thing "direction." After being sawn the stone is usually four-point, the saw marks running parallel to one the diagonals of a square formed by the grain. Failing paw marks, a four-point stone usually shows rough or lightly touched areas near the girdle, either above or below, these being disposed at the corners of an imaginary regular etagon. In a two-point mass the grain runs in one direc-tion across the table and there may be a distinct ridge. (90)