COLLINS S HARI.EY BINOCULAR. 



75 



chief drawback to the value of this instrument (in the Author's 

 opinion) is its not being furnished with a Stage-plate rotating 

 in the optic axis of the Microscope ; it would not be difficult, 

 however, to substitute the Nachet stage for the Mechanical stage 



Fig. 39. 



Collins's Harley Binocular. 



represented in Fig. 39 ; and such substitution would not merely 

 diminish the cost of the instrument, but would be (in the Author's 

 opinion) a real improvement.* 



* In addition to the Second-class instruments that have here been 

 noticed, others, alike Monocular and Binocular, may be mentioned as 



