G78 



SUMMARY OE CURRENT RESEARCHES RELATING TO 



Fig. 125 shows another purpose to which the Microscope can bo 

 applied in the workshop to obviate the difficulty often experienced in 



making accurate measurements 

 with callipers. B is a bar with 



a micrometer scale, fastened to 

 the right limb of a pair of 

 callipers, and a is an index 

 fastened to the left limb. The 

 work having been calibrated 

 in the usual manner, the posi- 

 tion of the index upon the 

 scale is accurately determined 

 by means of the Microscope A 

 which is also carried by the bar 

 I) ; and it is clear that in this 

 way a precision is secured which 

 is quite unattainable by the 

 ordinary methods of calibra- 

 tion. 



Finally the Microscope 



can with advantage be used to 



criticize the efficiency of the 



^^i^L- y emery wheel ; for this there 



is no better criterion than an 



examination of the fine dust thrown off at the edge of the wheel. 



If the cement is not hard enough, the particles of emery are soon 



loosened and removed ; if on the other hand there is too much hard 



Fig. 126. 



Fig. 127 



Fro. 128. 



