PROCEEDINGS OF THE SOCIETY. 
545 
opticians, was defective in the matter of the fine-adjustment — a most 
vital point in an instrument intended for critical work. Some five years 
ago, Messrs. Swift worked out a new and special system of fine-adjust- 
ment applicable to the Jackson model, which he had noticed at the 
time as being the most important improvement in that form of Micro- 
scope made up to that date. At that time the action of the mechanism 
was upon the nose-piece only, within the body-tube ; but later on it was 
found that the bearings, &c., could be more exactly fitted by arranging 
the mechanism to act on the whole body-tube, and that was the system 
adopted in the new Microscope. The great length and breadth of the 
bearing slides secured steadiness, at the same time providing ample 
space for the screw and long-lever action which could thus be made 
unusually strong and yet sensitive. The stage and substage supports 
were shaped as recommended by the late Mr. Tolies, of Boston, so as to 
be strengthened at the parts where they were attached to the stand. 
The mechanical movements of the stage seemed very elaborate, and 
whilst admitting the great convenience of having such movements, he 
thought the microscopist would do well to learn to manipulate without 
them ; or if that were too severe a task, then he thought his own 
mechanical stage — which moved the object about on the surface of the 
stage proper, without the intervention of moving plates — would be more 
serviceable, especially if strong clamping stage springs were brought to 
bear upon the slide when once got into the position required. The base 
and trestle supports of the Microscope were of unusual strength ; the 
two brass trestles supporting the trunnion axis were held together by a 
Y-piece after the manner of some of Troughton’s small transit instru- 
ments ; a third brass trestle supported the eye-piece end of the body- 
tube, the three trestles being screwed to an oblong brass base-plate 
pierced in the centre for the application of a clamping screw. The 
base-plate itself was fixed to a strong disc of mahogany — a sort of turn- 
table — having a tail-piece to carry the oxyhydrogen lamp, the whole 
rotating in or out of the axis of the camera, a stud-piece stopping it when 
in the axis, and the clamp-screw fixed it. The intention was that the 
microscopist would be seated, and would adjust the Microscope by 
rotating the instrument away from the camera, and then swing it in a 
line with the camera and clamp it. At the eye-piece end the trestle- 
support had a screw arrangement for collimating the optical image in 
the vertical direction on the centre of the focusing-screen. The frame 
carrying the focusing-screen was also provided with a small range of 
motion for centering the image. For photographic work the fine-adjust- 
ment screw was actuated by a system of pulleys and a silk cord kept at 
moderate tension by two straight springs ; a long rod on fittings at the 
side of the camera had an indiarubber ring on the cylindrical head, 
which engaged by friction on a large milled head connected with the 
silk cord. The motion was very smooth and regular. 
Without pledging himself to approve of every detail of the design, 
as being the best known arrangement, he thought Mr. Pringle was to be 
congratulated for his share in the production of the apparatus. Messrs. 
Swift had had a difficult task before them in constructing such an 
instrument, and they had accomplished their work in a most creditable 
manner. His own testing had been limited to the Microscope, especially 
the fine-adjustment, and he was glad to be able to say he found the 
1890. 2 Q 
