Sidle & Poalk's Acme Microscope

This microscope is the first cheap instrument that we have seen with a swinging substage. The general form of the instrument hardly needs any description, but it may be mentioned that the stage is made of two thin, circular brass plates, the upper one (shown in the left hand corner) fitted to turn upon the lower, so that the object can be rotated in the field of view. The stage can be centered. The upper plate can be removed, and two spring clips attached to the lower one, either above or below, thus making a stage for use with oblique light. The aperture in the stage has a standard screw thread to receive various accessories for illumination when it is desired to have the mirror move independently of them, and also to afford a means of mounting the selinite so that it can be revolved without turning the Nicol prism.

The mirror and substage are both attached by sliding fittings to the same bar, which carries them around the object as a center. The circular piece at right angles to the stage gives steadiness to the bar, with smooth movement, and is graduated to show the angular direction of the illuminating pencil. The horseshoe base is reversible, so that greater steadiness can be ensured when the stand is used in a horizontal position.