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SUMMARY OF CURRENT RESEARCHES RELATING TO 
adopted, it is confessed, with tlie wholly unnecessary object of having a 
stage large enough to carry cultivation-plates. 
M. Hartnack also exhibited a very remarkable photomicrographic 
apparatus, consisting of a Microscope in a horizontal position connected 
with the camera, which was on a stand supported by five levelling screws. 
The camera has some interesting peculiarities. The spindle which acts 
on the micrometer-screw fits into the centre of the support instead of 
being placed at the side, as in most instruments ; the pinion which 
transmits the movement to the screw-head of the slow motion, does 
not act directly, but through the intervention of a system ; the result 
of this is that the initial velocity given by the hand is considerably 
reduced, and accordingly the focusing is rendered more easy and 
precise. 
The firm of W. and H. Seibert exhibited several of their instruments, 
readily distinguished by their characteristic appearance from those of 
other makers. In these Microscopes the screw- head of the slow motion 
is at the top of the vertical column which supports the instrument. In 
the stand No. I. there are three motions of the body-tube, the coarse 
movement by rack and pinion, the ordinary slow motion with the screw- 
head below, and a third extra slow motion, for use with very high 
magnifications, in front of the column which supports the body-tube. 
To this model can be fitted either a rotating stage or one provided with 
rectangular movements. Their stand No. II. is similar, but does not 
possess the extra slow motion. Stand No. III. is smaller, but, like the 
others, it can be inclined and fixed at any angle, and is provided with a 
rotating stage, Abbe condenser, and iris-diaphragm. 
W. Watson and Sons, amongst other instruments, exhibited the 
Microscope, designed by Dr. Yan Heurck, which is described in this 
Journal, 1891, p. 399, and met with such severe criticism from 
Mr. Mayall. 
The firm of Carl Zeiss was very fully represented. Most of the 
large models, as well as the large photomicrographic and projection 
apparatus of this firm, have been described and figured in this Journal. 
One of the specialities of this firm is a sliding adapter. It consists 
essentially of a mortise slightly inclined in order to prevent displace- 
ment of the tenon on which the objective is screwed. This tenon is 
formed of two pieces, the lower one of which carries the objective, and 
can be moved from back to front by means of a screw. A second screw, 
fitted to the sliding piece, gives a movement from right to left. 
The firm of Carl Reichert exhibited several of their stands. The 
new large model la. is provided with a circular stage rotating on its 
axis after the English system. The movable stage, also for use with 
this model, admits of an exact displacement of about 25 mm. in two 
perpendicular directions. The stand II. is of simpler construction. 
In this model the illuminating apparatus is so arranged as to allow of 
the rapid change from illumination by the Abbe condenser to the 
ordinary illumination by the mirror. 
The stand No. VII. of this firm is a useful instrument for students, 
or even for the laboratory. The stage is circular and very large ; the 
micrometer-screw -is sufficiently good to allow of the use of immersion 
objectives. Perhaps the most remarkable point about this instrument 
