ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



657 



with two square openings of different sizes, which can be brought 

 successively over the silk under investigation, so that, as with the 

 ordinary " linen provers," areas of known extent may be under obser- 

 vation, and the number of strands to the metre or yard counted. 



The eye-piece has a conical cap for shutting off extraneous light. 



Sidle's No. 4 "Acme" Microscope.— Messrs. Sidle (U.S.A.) 

 have brought out a still simpler Microscope than the one figured and 



Fig. hi. 



described in vol. iii. pp. 522-3, embodying the swinging substage 

 with a minimum amount of " luxuries and intricate non-essentials." 

 The stand is shown in Fig. 141 (body 6z} inches long and 1^^ inch 



