Live-box.—This is a brass slide, perforated in the middle, to the aperture in which is soldered a short piece of brass tube, closed at the top with a circular plate of thin glass. A rather wider and longer piece of brass tube slides over the former; this is also closed at the top by a thin glass plate, so as to allow of an object being confined or compressed between the two glass plates. It is used for examining living objects in water.
Knife, &c.—For cutting slices or sections of objects, a very sharp knife with a thin back will be found useful; or a razor may be used for the same purpose. And for picking minute objects to pieces, or dissection, fine needles, cut off short with pliers, the blunt ends being thrust into hair-pencil sticks, will be requisite.
A pair of fine surgical forceps will also be required, for taking up minute objects. These should be without teeth, and the spring-action so weak that the points can be very easily approximated.
Dipping-tubes.—For removing minute objects from water, two or three narrow glass tubes, of different lengths, are very useful. These are called “dipping tubes,” and are used thus:—the tube being held upright between the second finger and the thumb, the fore finger is placed at the top of the tube to close it; the tube is then put into the water until the lower end is close to the object, when, on suddenly removing the fore finger, the water will rise in the tube, carrying the object with it. The fore finger is then again applied to the tube, and, as thus held, the water will not run out. The tube is then held over a watch-glass, or a slide, upon which the water and object will fall on removing the fore finger.
A small glass spirit-lamp will be found very useful. The spirit for burning should be methylated alcohol, or wood-naphtha. As these spirits are inflammable, great care should be taken to keep the stock-bottle away from a candle or other flame, when filling the lamp.
Achromatic condenser.—A very important piece of apparatus, when high powers are used, is the achromatic condenser; it is not, however, usually supplied with the cheaper microscopes. It consists of a brass fitting, placed beneath the stage, into which an object-glass is screwed, in an inverted position, i. e. the small end of the object-glass being placed uppermost. It serves to condense the light to a focus upon the object, so as to illuminate it more brightly; and as it can be elevated or depressed by a milled head and rack-work, the object can be viewed by either converging or diverging rays.
Simple microscope.—For examining the larger kinds of objects, and for dissection, a simple microscope is very useful. This consists of a stand, a stage, and an arm supporting a simple lens or combination of lenses, but without the body of the compound microscope (as the ordinary microscope is distinctively called). For most purposes, common plano-convex or doubly convex lenses are sufficient to form the object-glasses of a simple microscope. With the best microscopes, an “erector,” or tube containing a pair of lenses, fitted within the body, renders the compound microscope capable of answering most of the purposes of a simple microscope.
Polariscope.—An expensive but interesting and useful addition to a microscope is a polarizing apparatus, or polariscope. This consists of a Nicol’s prism, or a plate of tourmaline, placed beneath the stage, and another in the body of the microscope or above the eye-piece; both in brass fittings. The former is called the polarizer, and the latter the analyzer.
Rotating disk.—Another most useful piece of apparatus, for moving opake objects whilst under the microscope, in all directions, is Smith and Beck’s “rotating disk.”
Slides.—The slides upon which objects, especially those to be viewed as transparent objects, are to be placed, should be made of crown or plate glass. They are usually 3 inches long, and 1 inch wide; but I prefer them 2½ inches long, and 1 inch wide, simply because they take up less room in a cabinet, and because they do not project beyond the stage on either side. They should not be more than 1/20th of an inch thick, and as colourless and clear as possible. The edges should be ground or filed, to prevent their scratching the stage.