. The microscope; a simple handbook. Microscopes. 40 THE MICROSCOPE Parabolic refiector. Sorby reflector. Glass reflector. Vertical Fig. 30.—No. 3360, Parabolic Reflector. even when a moderately high power, such as a 1/6-inch (4-mm.) is used, because the band of light is sufilciently narrow to be directed through the small working distance between the object glass and the object. This method is particularly useful for the examination of alloys of metals or substances with fine laminse, as the heavy shadows shown by such oblique illumination indicate the character of the structure
. The microscope; a simple handbook. Microscopes. 40 THE MICROSCOPE Parabolic refiector. Sorby reflector. Glass reflector. Vertical Fig. 30.—No. 3360, Parabolic Reflector. even when a moderately high power, such as a 1/6-inch (4-mm.) is used, because the band of light is sufilciently narrow to be directed through the small working distance between the object glass and the object. This method is particularly useful for the examination of alloys of metals or substances with fine laminse, as the heavy shadows shown by such oblique illumination indicate the character of the structure. Another method of illuminating opaque objects is by means of a silvered parabolic mirror, which can be attached to either a 1^-inch (40-mm. or 32-mm.) or a 2/3-inch (16-mm. or 14-mm.) object glass. The front lens of the object glass being removed, the tubular portion of the reflector can be slid on to the cylindrical part of the object glass, which is of a standard size. This may be lightly clamped in position by the milled head and the front lens replaced. The object glass having been screwed into the microscope and focussed, the reflector, which has an adjustment up and down, shoxdd be placed so that its lower edge almost touches the object. The light should then be directed by a bull's-eye condenser in a horizontal direction parallel with the stage, so that it illuminates the whole of the reflector (Fig. 30). The reflector condenses it to a focus on the object, and a slight movement of the reflector up or down or a slight turn will give the best result. This produces a very brilliant illumination, and as the light falls upon the object from a large number of directions, the shadows produced are not, as a rule, misleading in interpreting structure. Mr. Sorby devised an addition to this reflector, which can be used with the 1^-inch (327mm. and 40-mm.) object glass, which consists of a small, flat, silvered mirror which swings in and out of the optic axis, and when it is in
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