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



saw would cut through steel. The glass should be cut half 

 way through and then reversed so that the final break will come 

 in the middle and thus prevent the edges from spawling off. 

 The chief defect of this machine was the way it scattered emery. 

 The disks are now ready for the grinding which is done on the 

 machine on the right of Fig. 3, which consists simply of a 

 vertical spindle run by a quarter twist belt from the counter 

 shaft against the wall. The end of this spindle is tapered at 



Fig. 3 



the upper end to receive the grinding tool or laps, shown on 

 the table in Fig. 5 which also shows the spindle raised so that 

 the grinding lap is seen above the tin box, C, which surrounds 

 the spindle to catch the abrasive that is thrown off in grinding. 

 The glass is first smoothed down on a flat lap until it is of equal 

 thickness at all points as measured by a micrometer when it is 

 ready to be ground to the ])ro])cr curves. For this purpose the 

 spherical laps, shown in Fig. 5, are turned in the special machine 

 illustrated in Fig. 4. The compound rest of an old Seller's 

 lathe was removed and in its place, on the cross slide of the 



