634 PROCEEDINGS OF THE AMERICAN ACADEMY. 



poor conductor, for the shorter horizontal bars, serves to insulate, as 

 well as to support and guide, the upper wire and spring. To prevent 

 lateral vibration of the long, or second, vertical arm of the " needle- 

 bar," a bearing is provided at the level of the table top of the machine, 

 as shown in Figure 2. 



The electric circuit used to heat the wire W is established by 

 clamping the wire of one pole to the head (Figure ?>, H) by a liinding- 

 screw (seen directly below the axle of the lever), and connecting the 

 other with the upper end of the insulated brass wire and spring. Thus, 

 head, lever, and bent "needle-bar" form a part of the circuit. In this 

 circuit is introduced a rheostat (R, Figure 3) consisting of some eight 

 or nine electric lamps of candle-power varying from 4 to 50, arranged 

 in multiple, each with separate key. These are seen in Figure 1, be- 

 neath the drawers at the right of the figure. A portable lamp on 

 the table (shown in Figures 1 and 2) is constantly in the circuit, 

 and serves to illuminate the wax plate while cutting. With an alter- 

 nating current of 110 volts the candle-power required properly to 

 heat the wire (W) — a platinum wire of 26 standard gauge (about 

 0.4 mm. in diameter) — is between 50 and loo. The rheostat de- 

 scribed allows one to adjust the resistance to any voltage ordinarily 

 used in electric lighting. 



The removal of the melted wax is effected by suction produced by 

 using a Bunsen pump. Figure 1 shows the machine set up with a pump 

 of the Richards pattern ; Figure 2, with a more efficient special pump, 

 made by Wagner und Muntz, Munich. With a pressure of 30 or 35 

 pounds either pump will effectually withdraw the melted wax. To 

 succeed with this suction apparatus, which is an essential part of the 

 outfit, requires careful attention to certain conditions. The sucking 

 tube must be hot enough to keep the melted wax from immediately 

 hardening, and it must be very close to the under surface of the wax 

 plate at the point where the plate is being cut. The manner in which 

 this has been accomplished is shown in Figure 3. A quarter-inch 

 (6 mm.) copper tube passes through a water reservoir heated with an 

 alcohol lamp, shown indistinctly in Figure 1. The lower end of the 

 copper tube ends in a glass bottle with an air-tight rubber stopper 

 pierced by a bent glass tube (D, Figure 3), to which the suction tube 

 from the pump (Figure 1) is attached. The tube is for the escape of 

 steam from the water tank. The upper end of the co})per tube is drawn 

 out into a bent nozzle (N, Figure 3, seen in vertical and in horizontal 

 section), with a narrow (about 2 mm.) orifice. In the convex side of 

 the terminal bend is cut a longitudinal slot (T), which is slightly wider 

 than the diameter of the platinum wire. The wire, without being de- 

 tached from its hooks, is slipped into the slot so as to occupy the centre 



