534 
SUMMARY OF CURRENT RESEAR6HES RELATING TO 
will be remembered that a sliding plate of powers was employed by 
<4. Lindsay * in bis simple Microscope, patented in 1743, but alleged to 
have been made as early as 1728. These are all the points to be re- 
Fig. 130. 
corded in this instrument ; it will, however, be of interest to compare it 
with that of Benj. Martin. 
In the optical part we noted that Benj. Martin doubled the field-lens 
* Journ. Quekett Micr. Club, vii. (1898) p. 115, fig. 22. 
