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CH. X] DRAWING WITH HOUSE CURRENT 345
§ 495. Microscope. — Any modern microscope with a good substage condenser can be used, provided it is supplied with a flexible pillar, so that the tube can be made horizontal; and provided also, that the fine adjusting mechanism will work when the tube is horizontal.
There must be a prism or mirror beyond the ocular to reflect the image-forming rays downward upon the drawing surface (fig. 192).
The discussion of avoidance of distortion, the proper objectives, oculars, etc., to use, which was given in the earlier part of this chapter apply here (§ 452, 483).
§ 496. Position of the microscope for drawing. — In the drawing outfits thus far devised, the microscope is placed in one of the following positions :
(1 ) In an inverted position with the objective pointing directly upward (as in the large Edinger apparatus, fig. 202).
(2) Inclined at 45 degrees (as in the small Edinger apparatus, fig. 204).
(3) In a horizontal position (fig. 192).
With the microscope in an inverted, vertical position, there should be no distortion of the image if the drawing surface is horizontal.
With the inclined microscope, the mirror used must be so inclined that it throws the image directly down upon the horizontal drawing surface, or the image will be distorted. It is not easy to tell just the inclination of the microscope, and therefore, the exact inclination to give the mirror, to make the axial ray perpendicular to the drawing surface. In the small Edinger apparatus (fig. 204), the directions are to make the inclination of the microscope 45 degrees and the inclination of the mirror 22^" degrees. This arrangement will give a correct image. One may need to use a protractor to make sure that the inclination of the microscope and mirror are exactly correct.
With the horizontal microscope, the mirror or prism is so arranged that it is fixed at 45 degrees and therefore if put directly over the ocular of the horizontal microscope, will reflect the light perpendicularly upon the drawing surface, thus avoiding distortion (see § 483).