Description of a Museum Microscope

Abstract

ABSTRACT In the annual address to the Microscopical Society I drew attention to the importance of familiarising the public with the use of the microscope, in order that they may become acquainted with its applications. One great barrier to its use in museums has been that, as usually constructed, it has been easily displaced, put out of order when adjusted, or its parts could be removed fraudulently. These evils could only be remedied by the constant presence of a skilful and watchful attendant. In order to obviate these difficulties I have had a microscope constructed, of which the accompanying figures will give a good idea. The first object to be secured was that of the fixity of the whole instrument. This has been effected by attaching the stand, e (figs. 1 and 2), to a block of wood. Fig. 1 is intended for viewing transparent objects, and the stand is fixed at an angle of about 59°. Fig. 2 is intended for viewing opaque objects, and the stand is made upright. The block, h, to which the stand is affixed, may be screwed to a table, shelf, or other fixed object, where there is a good light, by a couple of screws from the bottom. This arrangement secures the instrument from being knocked over. The eye-piece, a, is placed in the tube in the ordinary way, but by means of a slit at the back of the tube, which admits of the movement up and down of a screw attached to the eye-piece, it is fixed at any point which may be thought desirable. This screw, b, is only moved by the aid of a screw-driver. This secures the immovability of the eye-piece. As a matter of experience, I may state that the screw needs to be very strong, as persons having a little knowledge of the microscope, and wishing to display it, have made violent efforts to remove the eyepiece, which of course is intended to be fixed. The object-glass, d, is attached to the tube, and is also secured by the aid of a screw. Thus the only movement permitted to the tube of the instrument is performed by a screw, e, which moves the tube in the way of the fine-adjustment of the ordinary microscope. As moveable slides would be liable to accident or to be purloined, two forms of slide which are not removeable from the microscope have been supplied. These are fixed in the position usually occupied by the stage, f. The slide for transparent objects is circular, and is made of wood, and has holes bored for the reception of eight pieces of glass on which the object is placed. A piece of thin glass is then put over this, and the whole kept in position by an elastic metallic ring. The slide revolves on a metal screw, which, is attached to the holder, i, and which occupies the place of the stage. By this means eight, ten, or more objects may be mounted at the same time, and brought under the object-glass by merely moving the circular slide. The compound slide for viewing opaque objects (Fig. 2f) is constructed on a somewhat different plan. It is a frame into which the common glass slides, three inches by one, can be pushed, and when it is filled up they are secured by means of the screws, k. The slides in their frame are then made to move backwards and forwards in a frame attached to the arm, i, which is situated in the place of the ordinary stage.