506 



RECORD OF CURRENT RESEARCHES RELATING TO 



Fig. 33. 



the next smaller punch, leaving it flat and true. The three rings (Fig. 

 30) thus prepared are suitable for use with cover-glasses of one-half 

 inch, five-eighths inch, and three-quarters inch diameter. They may 

 be fastened to the slide by a little warmth and pressure only, or 

 by some kind of cement, which will not only form a coating to the 

 wax, but also secure it to the slide. 



Of instruments adapted to cutting both wax and sheet-lead cells, 

 two very convenient forms were brought forward by Dr. E. H. Ward, 

 at a recent meeting of the Troy Scientific Association. The first was 

 designed by Mr. C. M. Vorce, of Cleveland, O,, and is represented in 

 front view and in section in Figs. 31 and 32. It can be readily made 

 by amateurs for their own use. It consists of a wooden body of such 

 size as to be easily held and twirled between the fingers, with a short 

 needle point inserted in the centre of the lower end. On one side a 

 longitudinal slot or groove is cut through the wood deep enough to 

 allow the cutting edge to approach nearly to the needle. The cutter 

 should be ground to a triangular point, and ground only on the out- 

 side, leaving its inner face flat and smooth. A screw passes through 

 the body of the instrument, and bears against 

 the spring, regulating its distance from the 

 needle point. Greater firmness might be secured 

 by changing the form of the body so as to sup- 

 port at its two edges the cutter when forced out 

 to its farthest limit. 



The other instrument, shown in Fig. 33, 

 was suggested by the Vorce instrument, and was 

 contrived by Mr. F. Eitchie, of Troy. It pos- 

 sesses greater power and precision than the other, 

 but is not so easily made by an amateur. It 

 consists of a pair of spring dividers about three 

 and a quarter inches long, from one leg of which 

 half an inch of its length has been cut off and 

 replaced by a brass socket with a binding screw 

 to hold a small knife-blade. A knob is also 

 added at the top for convenience in manipulation. 

 The method of working these two forms of 

 apparatus is precisely the same. A sheet of wax 

 may be laid on a sheet of heavy white paper, and 

 both together tacked to a piece of smooth hard 

 wood. The instrument, with its legs set three- 

 sixteenths inch apart, is used to cut out a series 

 of disks of three-eighths inch diameter. How 

 near together these can be safely cut will soon be 

 learned by experience. The legs are then set 

 one-quarter inch apart, and using the same centres as before, a series 

 of rings can be cut suitable for one-half inch covers. By succes- 

 sively spreading the legs one-sixteenth inch further each time, rings 

 may be cut around the same centres for five-eighths and three- 

 quarters inch covers, and larger if desired. The concentric rings 

 around each centre are cut out without waste, as shown in Fig. 30. Not 

 only wax, but also sheet lead, cardboard, and guttapercha can be cut 



