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The Ohio Journal of Science [Vol. XVI, No. 1, 



costing as much as fifteen dollars. This glass comes in slabs, 

 but will be cut by the makers with either a diamond saw or a 

 sand saw, the purchaser paying for the "saw dust." 



The slabs that were used here were 2" x 6" x Y/ and the 

 first operation was to cut from these round disks a little larger 

 than the finished lens. This was accomplished in the following 

 manner and is illustrated in Fig. 1. In the chuck of a drill 

 speeder on a. Barnes drill press was placed a 34" steel rod which 



Fig. 1 



Fig. 2 



carried at its lower end a copper tube, A, which was steadied at 

 the bottom by a steel washer, bored to a loose fit to the tube, 

 and clamped to the glass as shown. Number 40 Carborundum 

 was used and lubricated with plenty of water. The tube must be 

 lifted frequently to allow the abrasive to flow to the cutting 

 edge. This is done so often that it seems almost a continuous 

 motion of lifting and pressing down again, the tool resting on 

 the glass hardly more than two or three seconds at a time. 

 The cutting may be done at such a speed as to allow of a slight 

 heating. As soon as the tube has cut itself about a sixteenth of 

 an inch into the glass, the guiding washer may be removed and 



