ZOOLOGY AND BOTANY. MICROSCOPY, ETC. 
421 
attached and removed in a few seconds ; (2) it is movable in the trans- 
verse direction and from back to front ; (3) it can be adjusted by one 
hand only. It has the following arrangement : — The fixed stage is 
traversed in the middle from back to front by a rectangular slit Y 
(fig. 50), about 1 cm. wide, which extends from the column of the slow 
movement up to about 1 cm. from the aperture of the stage. In this 
slit is a horizontal micrometer screw Y (fig. 51), which is provided on 
the extremity at the back with a vertical-toothed wheel P, working 
in a horizontal toothed wheel R, which is mounted on the column of the 
slow movement. The wheel R effects the movement of the micrometer 
screw V, while the latter acts on a small carrier C, which is flush with 
the stage, and, guided by the bevelled edges of the slit, traverses it from 
back to front. The movable stage is attached to this carrier by four 
vertical pins which fit into four corresponding holes in the carrier. It 
consists of a carrier movable in the transversal direction by means of a 
long micrometer screw terminated at each extremity by a screw-head P 
(fig. 50). Attached to the carrier in front is a plate M (fig. 51) cut away 
considerably in the centre in order not to hide the aperture of the fixed 
stage in any of its positions. This plate slides on two blunt ivory 
points, and the preparation is held firmly upon it by two small clips. 
In the adjustment of the stage, the lateral movement is effected by 
the screw-head P on the right, which is held between the thumb and 
first finger of the right hand, while the movement from back to front is 
produced by tbe simple pressure on the wheel R of the thumb, which 
can be bent back without displacing the hand. 
The two carriers are provided with scales graduated in millimetres, 
with verniers reading to 1/10 mm. 
The slide containing the preparation under examination has its 
position fixed by being fitted into a sort of rectangular box in which only 
two sides are retained, viz. the back and left. 
The transverse displacement is not of sufficient extent to allow of 
the examination of the whole length of a slide. To meet the case, 
however, when the preparation happens to be mounted at the end of the 
slide, the back edge of the rectangular box which holds the slide is 
dovetailed in a sliding piece, so that it can be displaced laterally by 
simple pressure of the fingers, and take three positions marked by a 
catch. 
The author mentions, in conclusion, the Nachet eye-piece with very 
large field, and a convenient accessory to this in the shape of a small 
hood which can be placed over it. It is provided with a deep conical 
groove in which there fits a piece of black card, so cut as to protect the 
eye from external rays of light. 
A new Fine -adjustment for the Substage. — Mr. G. C. Karop 
writes to us: — Every microscopist who works with modern high powers 
of large N.A. in combination with wide-angled condensers, soon becomes 
aware that the usual focusing arrangements of the substage are not 
sufficiently delicate ; for it is necessary, if the best possible resolutions 
are required, that the image of the flame given by these condensers, 
whether dry or immersion, should be as accurately adjusted in the focal 
plane as the object itself. Although this is well understood, there are, 
so far as I am aware, but few devices for the purpose of obtaining this 
