Standard Gauges for Eyepieces 



83 



No. 4. is the maximum size for long tube binoculars. 



It will be admitted that the makers here have an excellent 

 choice of gauges for their instruments, and it is eminently 

 desirable that eyepiece fittings be confined absolutely to 

 these sizes. For many years it has been the rule with 

 certain houses for reasons of their own to make draw-tube 



Fig. 23. — Zeiss's Binooular Eyepiece. 



fittings of diameters which do not conform to either of the 

 above-mentioned standards, and those who may be contem- 

 plating the purchase of a microscope will be conferring a 

 benefit on microscopy generally and directly on themselves 

 if they insist that the microscope they select shall have one 

 or other of the standard sizes of fittings for eyepieces, and 

 refuse to accept any other diameter. 



6—2 



