ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
113 
of the makers. Many instruments in which this mode of adjustment is 
used are faulty, either from the socket being somewhat oval, or from tho 
lower opening being wider than the upper. The movement of tho body- 
tube in the socket is also generally much too hard. 
Fig. 4. Fig. 5. 
An improvement which the author has devised consists in replacing 
the ordinary small and thin ring for the manipulation of the body-tube 
by a much larger one. This (tigs. 4 and 5) consists of a round disc, 
2 in. in diameter, which is surrounded by a hoop, 1 in. broad, and 
Fig. G. 
provided with a milled edge. By this device the movement of the body- 
tube is rendered much more smooth and certain, as the result of which 
the author has noted that with this modified tube much fewer cover- 
glasses are broken by beginners. 
1896 I 
