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CH. X] DRAWING WITH CAMERA AND MICROSCOPE 333
it some tracing paper. By covering the head with a focusing cloth to shut out the surrounding light, one can trace the outlines of the object on the tracing paper, and transfer these to ordinary drawing paper, and proceed to ink them in and give the shading necessary free-hand.
With the magic lantern or with the opaque lantern the image is projected upon the drawing surface and regular drawing paper can be used to make the original pencil tracing upon, but with the camera one must use translucent paper for the tracing and then transfer it to the drawing paper. (To get an erect image with translucent paper see § 519).
DRAWING WITH THE PROJECTION MICROSCOPE
§ 472. Range of objects. — For drawing as for projection it is exceedingly desirable that the projection microscope should enable the investigator to commence where the magic lantern leaves off, and to carry the work to its utmost possibilities; that is, beginning with large specimens of 50 to 60 mm. (2 in.) in diameter requiring low objectives, and going on from this to the smallest objects visible and using the oil immersion objective at the other extreme.
To realize this ideal possibility one must have available for drawing some such outfit as that described in Ch. IX for projection ; and in addition suitable arrangements for reflecting the image down upon a horizontal drawing surface. Fortunately, the additions are relatively simple and inexpensive.
Finally, for the widest usefulness in drawing there must be the possibility of using the ordinary house electric lighting system for an electric lamp with small carbons (see § 486).
§ 473. Drawing large objects with low powers. — For this it is necessary to have a stage with a large opening (fig. 134), and the objective must be mounted in a shield with no tube at all (fig. 138), or the tube must be short and of large diameter, so that the field is not restricted (fig. 137). Finally, there must be some means of increasing or diminishing the distance between the objective and the drawing surface to get the desired magnification.