. The microscope and microscopical methods. Microscopes; 1896. CH. VIII.} PHO TO-MICROGRA PHY. many workers find the only opportunity for work. Following the sunlight, the electric light is the most intense of the available lights. Then comes magnesi- um, the lime light, the gas-glow or Wellsbach light, and lastly, petroleum light. The last is excellent for the majority of low and moderate power work. And even for 2 mm. homogeneous immersion objectives, the time of exposure is not excessive for many specimens (l% to 3 minutes). This light is also cheapest and most available. Fig. 148. Vertical
. The microscope and microscopical methods. Microscopes; 1896. CH. VIII.} PHO TO-MICROGRA PHY. many workers find the only opportunity for work. Following the sunlight, the electric light is the most intense of the available lights. Then comes magnesi- um, the lime light, the gas-glow or Wellsbach light, and lastly, petroleum light. The last is excellent for the majority of low and moderate power work. And even for 2 mm. homogeneous immersion objectives, the time of exposure is not excessive for many specimens (l% to 3 minutes). This light is also cheapest and most available. Fig. 148. Vertical Photo-Micrographic Camera furnished by the Bausch & Lomb Optical Company. {From the ijlh edition /S96) of their Catalog.) EXPERIMENTS IX PHOTO-MICROGRAPHY. § 334. The following experiments are introduced to show practicall}' just how one would proceed to make photo-micro- graphs with various powers, and be reasonably certain of fair success. If one consults prints or the published figures made directly from photo-micro- graphs it will be seen that, excepting the bacteria, the magnification ranges mostly beween 10 and 150 diameters. The technical difficulties in making good photo-micrographs of animal tissues at a greater magnification are so great that, while they may be used as the basis for figures, \\\<ty are, in most cases not suit- ---"- J -L able for direct reproduction. Photo-Micrographs at a Magnification of 5 to 20 Di- ameters.—In the study of embryology and the morphology of small animals or of individual organs like the brain, it is frequently desirable to make pictures of the whole object in its natural setting. These ob- jects and their surroundings are frequently from one to two centimeters in diameter, that is of a size too great to be satisfactorily photographed with microscopic objectives. In common with other observers the writer has found the short focus, wide angled, photographic objectives to give excellent results. It is necessary to have c
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