which is fitted an adjustable Ramsden eyepiece. Within 

 is a frame carrying one or several delicate spider lines, 

 which are moved across the space to be measured by 



Fig. 59. 



an accurate screw of either 0.5 mm. or 1-50 inch pitch, 

 which has at its end a graduated disc divided in 100 

 or more spaces, thus giving a definite value for each 



Field of Filar Micrometer. 



space. An adapter is also provided for attaching to 

 the tube of the microscope. 



181 



