ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
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piece. Finally, the two pieces fitted together are traversed by the 
clamping-screw for the inclination. 
The stage rotates, and special means are provided to give a very 
smooth movement, and at the same time to secure perfect firmness in 
every position without the necessity for any toothed gearing, which 
seldom works smoothly for any lengthened period. The mechanical 
movements are effected by two superposed plates, as in the old Ross 
stands, actuated by lateral screws. The object rests upon a sliding bar 
provided with a stop-pin and clamping-screw. For ordinary work the 
sliding bar can be replaced by a fixed plate provided with two ledges. 
The horizontal and vertical movements have a range of 25 mm., and 
the divided scales (finders) allow a reading of the movements to 1/10 mm. 
by means of verniers. 
The limb incloses the fine-adjustment and carries the tube in front ; 
both the coarse- and fine -adjustments move in bearings which can be 
regulated as required. A screw attachment at the upper part of the 
limb fixes the instrument firmly in the horizontal position when it is 
required to photograph in that position, though we infinitely prefer 
photographing with the Microscope in the vertical position. 
The fine-adjustment is of exquisite delicacy and of greater precision 
than that of any other Microscope in our collection. Each turn of the 
screw of the fine-adjustment corresponds to 1/13 of a millimetre. So 
perfect is the adjustment, that it is possible in certain cases to estimate 
to a hundredth of a turn, i. e. to 1/1300 of a millimetre. The mechanism 
of the fine-adjustment acts in an opposite direction to that of Conti- 
nental Microscopes, we have therefore marked on the milled head the 
letters M ( monter ) and D ( descendre ), to indicate the direction in which 
it is necessary to turn to make the body-tube move up or down. 
The body has a draw-tube ; when closed up it has a length of 160 mm., 
which is necessary for the employment of Continental objectives ; when 
drawn out it has a length of 260 mm. and can then be used for the 
apochromatics for the English tube. The draw-tube is arranged so 
that it can be blackened internally over part of the space covered by the 
eye-piece ; thus all internal reflection, which is the cause of so much 
trouble in photomicrography, is absolutely prevented. It might be 
preferable to line this tube with black velvet. The lower end of the 
draw-tube is provided with the Society screw for use with the Abbe 
aper tome ter. 
The mirror is carried by a rod having lateral movement ; it can also 
be slid up or down within a moderate range. 
Regarding the substage, which we have designedly reserved to the 
last, we have to point out some improvements which have not been 
introduced in any other Microscope. Needless to say, the condenser can 
be centered, and it can be raised anv* lowered by rack and pinion ; but a 
fine-adjustment of great delicacy is also applied. In the few Micro- 
scopes to which a fine-adjustment of the condenser has hitherto been 
applied (an adjustment so necessary in certain cases and not yet suffici- 
ently appreciated) this focusing has been simply effected by a screw 
which does not produce a very slow movement, and there has always been 
loss of time in the changes of direction. Here, however, the fine-adjustment 
is actuated by a lever as in the fine-adjustment of the body-tube, and 
