ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
97 
Messrs. Swift and Son’s Improved Dick Petrological Microscope. 
— The original form of this stand was described by Mr. Allan B. Dick in 
this Journal in 1889, pp. 432-6, fig. 57. The present instrument 
i(fig. 6) differs from the ordinary Dick model in haying an independent 
revolving stage, which allows the object to be revolved in the field of 
the cross-wired eye-pieces; whereas in the first stand the object re- 
mained stationary, and the eye-piece revolved instead. 
In the present stand an achromatic convergent system is provided, 
the upper lens of which slides in and out of the centre of the stage for 
use with high and low pov\ers ; being flush with the surface of the stage, 
it is always in contact with the object, and when an immersion fluid is 
used it gives an angle of 1*05. The lower lenses of the system are 
moved up or down by a revolving collar. The convergent system can 
easily be adapted as a spot-lens for any objective from 2 in. to 1/8 in. 
Immediately below the system, and above the polarizer, is a small 
iris diaphragm. The polarizer is made to swing out of the axis of the 
Microscope to allow the achromatic condenser to be brought into use. 
The nose-piece is a self-centering one. The upper horizontal slide E has 
a revolving diaphragm of apertures for viewing rings and brushes in 
minute crystals. 
Messrs. W. Watson and Son’s “Grand Model” Van Heurck 
Microscope. — This instrument (fig. 7) is constructed on similar lines to 
Messrs. Watson’s “ B ” Van Heurck Microscope figured in this Journal 
(1893, p. 92), but possesses the following special features : — The stage has 
rectangular mechanical movements, controlled by two stationary milled 
heads, working on one centre ; 1 in. of motion is afforded to the stage 
plates in either direction. The whole stage can also be completely 
rotated in any position. The base-plate carrying the stage is continued 
in one casting round the sides of the 1 mb and fixed by screws, instead of 
being screwed to the front of the limb as in the ordinary way, and the 
bolt on which the instrument is inclined goes through the whole — limb 
and stage supports — thus imparting unusual firmness. In order to in- 
corporate these alterations an increase of size of the Microscope has been 
necessary, and all the parts are more massive than in the original stand. 
The tripod foot is cork-shod, and has a spread of over 10 in. in each 
direction. 
Zeiss new Mechanical Stage for Stand la. — For this stand Messrs. 
Carl Zeiss have recently constructed a mechanical stage which differs 
from that formerly supplied by them. The object in designing this new 
type of stage was to obtain, without diminishing its size and the exact- 
ness of its movements, an instrument of such solidity as to admit of its 
being permanently left on the Microscope and thus rendering the use of 
a separate stage superfluous. 
The object-slide is placed in the usual manner with its shorter edge 
against the left stop A (fig. 8) and the left end of the lower long edge is 
pressed against the frame ledge R. The other stop B, which slides in a 
slot, is then placed against the other edge of the slide so as to hold it 
firmly. Stop A may by means of a screw h and a set pin be fixed at 
different points of the frame, there being a series of holes provided 
1895 H 
