554 



Notes. 



groove beneath the main stage, following the plan previously adopted 

 by Powell and Ross. The foot and pillar are unaltered. This is a 

 carefully made and well-finished Microscope. The accompanying ob- 

 jectives are peculiar, and need explanation. There is a lh in., over 

 the front of which a diaphragm is placed ; when a higher power is 

 wanted, the diaphragm is removed and a front is substituted for it, 

 the combination thus formed being of 8/10 focus. To make a 1/2 in. 



Fig. 149. 



this front is exchanged for another one. This 1/2 in. front has 

 a correctional collar graduated into ten divisions. The 1/4 in. is 

 a complete objective in itself with a similarly graduated correctional 

 collar. These were the first two correctional collars to be so graduated, 

 and it was some years before this excellent plan was adopted by other 

 makers, as they considered that two lines, marked covered and un- 

 covered, were sufficient for the purpose. Lieberkuhns were supplied 



