SECTION V. _On the Photographic delineation of Microscopic objects._ Many specimens of Micro-photography which have been exhibited are exceedingly elaborate and beautiful; and their production is not difficult to one thoroughly acquainted with the use of the Microscope and with the manipulations of the Collodion Process. It is important however to possess a good apparatus, and to have it properly arranged. The object-glass of the ordinary compound Microscope is the only part actually required in Photography, but it is useful to retain the _body_ for the sake of the adjustments, and the mirrors used in the illumination. The _eye-piece_ however, which simply magnifies the image formed by the object-glass, is not necessary, since the same effect of enlargement may be obtained by lengthening out the dark chamber, and throwing the image further off. _Arrangement of the Apparatus._--The Microscope is placed with its body in a horizontal position, and the eye-piece being removed, a tube of paper, properly blackened in the interior, or lined with black velvet, is inserted into the instrument, to prevent irregular reflection of light from the sides. A dark chamber of about two feet in length, having at one end an aperture for the insertion of the eye-piece end of the body, and at the other a groove for carrying the slide containing the sensitive plate, is then attached; care being taken to stop all crevices likely to admit diffused light. An ordinary Camera may be employed as the dark chamber, the lens being removed, and the body lengthened out if required by a conical tube of gutta-percha, made to fasten into the flange of the lens in front. The whole apparatus should be placed exactly in a straight line, that the ground glass used in focussing may fall at right angles to the axis of the Microscope. The length of the chamber, measuring from the object-glass, may be from two to three feet, according to the size of image required; but if extended beyond this, the pencil of light transmitted by the object-glass is diffused over too large a surface, and a faint and unsatisfactory picture is the result. The object should be illuminated by sunlight if it can be obtained, but a bright diffused daylight will succeed with low-power glasses, and especially when Positives are taken. Employ the concave mirror for reflecting the light on the object in the latter case; but in the former the _plane mirror_ is the best, except with powers exceeding a quarter of an inch, and of large angular aperture. The image upon the ground glass should appear bright and distinct, and the field of a circular form and evenly illuminated; when this is the case, all is ready for inserting the sensitive plate.