Radial Research Microscope.

The Radial microscope in its complete form (No. 3190) is a universal instrument for research. The general design is that of a small optical bench, which is swung in a concentric fitting, so arranged that as the instrument is changed from the vertical to the inclined or horizontal position, the centre of rotation is in the optic axis, and the centre of gravity always lies near the centre of the base. This arrangement combined with the focussing stage which the instrument possesses, is of special importance for metallurgical work where a vertical illuminator is used, as the illumination, once having been set, is not altered by the inclination of the instrument or by the focussing.

The instrument has a heavy base with two uprights in which the limb swings in grooves. The limb has a parallel dovetailed slide provided with a rack along its entire length, and all the parts of the microscope fit this dovetail and are moved upon it, and with the exception of the mirror slide, are actuated by racks, pinions and milled heads. Upon the upper part of this slide is fitted the body of the microscope with its fine adjustment. In a position near the middle is fitted the stage and substage which are in one unit. The lower end of the main slide carries the mirror.

The rack and pinion actuating the body forms a coarse focussing adjustment. The body fitting also carries the nosepiece, which, actuated by a double lever action, forms the double speed fine adjustment, which is operated by two side milled heads each giving a different speed. The slow motion slide only carries the object glass and does not support the weight of the body,

The body fitting has a square hole down its entire length, in which fits a bar. At the upper end of this bar is fitted a bracket to which a telescopic drawtube is attached. By means of a rack and pinion this drawtube can be raised for a distance of 2^ in. Also by means of the telescopic tube it can be raised further giving a variation in tube length of from 110 to 250 m/m. This bar and its drawtube can be completely removed and replaced by a high power binocular body. Apparatus such as a spectroscope or a small camera can be attached to this bar and drawtube. There is no fear of upsetting the fine adjustment by the attachment of these pieces of apparatus, as the fine adjustment mechanism works quite independently, these other pieces of apparatus being separately supported.

A Greenough binocular can be supplied on a separate carriage which fits in the main dovetail slide of the microscope.

The stage slide consists of a focussing carriage, the upper portion of which carries the stage and the lower portion of which carries the substage. Two forms of stage are supplied : one is the square stage as fitted to the Massive microscope, and the other is the complete circular rotating stage with centring motion as described on page 84. The square stage is cut out in the front to enable the substage apparatus to be readily changed. The substage focusses by rack and pinion and has centring adjustment, and consists of a cylindrical fitting of the R.M.S. standard diameter. It also has a dovetailed slide similar to the system adopted in the Massive microscope, so that an achromatic condenser or a dark ground illuminator can be permanently centred upon its respective slide and can be interchanged without altering the position of the substage.

The petrological apparatus is on the well known “ Dick ” principle, by which the polariser and analyser are rotated together, the angular rotation being read on a scale on the analyser. The mechanism has been improved b}? the substitution of direct acting links for cog wheels, and also a great improvement has been made in working the fine adjustment independently of this apparatus, which in the older models, owing to its weight, put considerable strain upon the fine adjustment.

A simpler form of Radial research microscope is also made (No. 3192). In this the body fitting has a different arrangement for the fine adjustment slide which carries the whole body. The arrangements for carrying the various interchangeable bodies is not provided and the petrological apparatus cannot be fitted.

For full description of the Radial microscope and its use see “ The Microscope : an Advanced Handbook,” by Conrad Beck, price 7/6 net.

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