ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



715 



its place by four upright rods which pass down through the base and are 

 fastened by nuts, both on the lower side of the base and on the upper 

 side at the too. 



The instrument is furnished with fine adjustment only, and the milled 

 head is removed, allowing the top of the case to rest on the head of the 

 support. The square head of the micrometer-screw projects through a 

 small aperture in the plate, and is manipulated by a detachable key kept 

 by an attendant. The upper end of the Microscope body is provided 

 with a clamping-ring which fixes the tube immovably in its place. The 

 ocular is likewise fastened by a set-screw. All joints and openings are 



Fig. 186. 



sealed with felt in such a manner as to be dust-proof. The instruments 

 are fitted with ocular ii. and objective 3, giving a magnification of 70, but 

 this combination may be changed from time to time. Fig. 185 is a 

 sectional view of the case. The instruments are fastened in pairs to 

 tables of special design (fig. 186), and the objects placed under observa- 

 tion aid in the illustration of exhibits in the cases. Suitable explanations 

 are given by labels placed on the tables at the side of the instrument. 

 The tables are furnished with heavy iron sills to secure stability, and 

 hold the instruments at a height above the floor convenient for the use 

 of the majority of observers. 



"London" Microscope. — Figs. 187, 188, represent the "London" 

 Microscope exhibited by Messrs. E. and J. Beck (Ltd.) at the Meeting 

 of the Society on November 21st. There is no special novelty in the 



