Satisfactory grinding may be carried out by the use of copper or type-metal cones for the preliminary shaping. Such cones should be mounted on a mandrel which will fit into the chuck of the American hand-drill and turned on the lathe to the desirable angle for stoppering. A number of these cones will be necessary. A number of similar moulds, that is to say blocks of type-metal or hard lead in which is a hole corresponding in size and angle to the plug desired, should be made also. These must be rotated, either in the lathe or by other means, and are used for the preliminary shaping of the plug. If but few plugs are to be ground it is unnecessary to provide a means of rotating the moulds, as the plug may be held in the hand and ground into the mould in a manner similar to that used in the first method of stoppering. [Illustration: Fig. 14] When the socket and plug have been ground, by the successive use of cones and moulds, to the desired angle, so that they correspond almost exactly, the plug is given its final fitting into the socket by grinding-in with a fine abrasive, in the manner first described. _Stopcocks._--Although it would be more strictly in keeping with the form of this book to divide the making of stopcocks into two parts; shaping by heat and grinding, we will consider the whole operation here, and take for our example a simple stopcock such as that illustrated by Fig. 14. The "blank," _f_, that is the socket before grinding, is made by drawing out a piece of fairly thick-walled tubing into the form shown by _a_. Two zones on this tube are then heated by means of a small, pointed flame, and the tube is compressed along its axis, thus producing two raised rings as shown by _b_. Two zones, slightly towards the outer sides of these two raised rings are heated and the tube is drawn while air pressure is maintained within. This produces two thin-walled bulbs or extensions similar to those shown by _c_. One of these extensions is now broken off by means of a sharp blow with the edge of a file or other piece of metal, and the edges of the broken glass are rounded in the flame. The other extension is left to serve as a handle. We have now a piece of glass like that shown by _d_. Now heat a spot on the side of this, medially between the raised rings, until the glass is on the point of becoming deformed, and bring the intensely heated end of a smaller tube in contact with the heated spot. Without disturbing the relative positions of the two tubes, press the smaller tube down on a thin steel wire, so that the wire passes along the tube and enters the soft glass; thus forming a projection inside the sockets as shown by _e_. The wire must be withdrawn, again immediately. When the wire has been withdrawn, heat the place where it entered to dull redness, in order to relieve any strain; break off the thin extension, which up to the present has served as a handle, round off the broken edges in the flame, and join on and