Stands A. and I. are fitted with a new fine adjustment device (one division on the micrometer screw corresponding to 1/1000 mm.) which is fully described on pages [25-26].
5. The tube of the microscope encloses a second tube, or draw-tube, which latter carries the eye-piece, and is so graduated as to indicate the exact length of tube in use at any time. The lower end of the tube has a thread into which the various objectives or a nose-piece screw. Tube and objectives are provided with the so-called "Society screw".
The nose-piece has now become an almost indispensable part of a working microscope. It can, however, be used to best advantage only on such stands as are provided with a coarse adjustment by rack and pinion. Aside from the advantage derived from the rapid changing of objectives, which it permits, it is so accurately made and centered as to materially facilitate the focussing of the various objectives. It is only necessary to focus with the fine adjustment to obtain a view of the same microscope field which had been under observation before the change was made.
As it is necessary for this purpose that the objectives should be accurately adjusted to the nose-piece, it is very desirable that in ordering an instrument its nose-piece should be ordered at the same time if one is to be used, as subsequent ordering may necessitate the return of the stand and objectives to us.
Stands A, I, Ia, Ib, II, IIa, IIb and III are those which are best suited to fine microscopical investigations. Among them the physician and bacteriologist will find an instrument entirely suited to his particular needs.
Stand III is now provided with rack and pinion adjustment.
Stands IV and V are small instruments, which serve nevertheless many purposes where the more elaborate outfits are unnecessary. They make excellent laboratory stands for elementary courses in microscopy.
In Stands IV and V the coarse adjustment is by means of sliding tube. They are all provided with fine adjustment by micrometer screw.
Stand VI is provided with rack and pinion adjustment only. It has a large stage, and is particularly intended for searching for trichinae and for similar examinations where a very strong durable stand is desired and where the use of high power objectives is unnecessary. It may also be useful as an auxiliary stand for purposes of demonstration in laboratories.
Stands III, IV, V, VI have no joint for inclining the body.