214 



PHO TO-MICROGRAPH Y 



[CH. VIII 



§ 350. — Objectives. — For making pictures from one to five times 

 natural size objectives of 60 to 100 mm. focus answer well (Figs. 1 76— 

 180). Short focus (75 to 100 mm. equivalent focus), wide angle pho- 

 tographic objectives are also admirable for this work. 



V 



42. 



E.LE 

 WET 



1 



~y. 



f""^ "l 



nil' 1 ; 



!TI, 

 LAR 





Fig. 178. Fig. 179. 

 Fig. 178. Leitz 64 millimeter ob- Fig. 179. Leitz 42 millimeter ob- 

 jective for photography and for projec- jective for photography and for projection 

 tion ( Wm, Krafft, N. Y.) ( Wm. Krafft, N. Y.) 



P'iG. 180. Zeiss' Apochromatic Projection Objective of 70 

 mm. equivalent focus, for photo-micrography. (Zeiss' Catalog.) 

 This, and another of 35 mm. focus, are designed for making 

 8 pictures of moderate magnification. Usually rather large ob- 

 jects -are photographed with them. The object may be illumina- 

 ted in the ordinary way. They are used without an ocular, 

 like a photographic objective. The one of 35 mm. is screwed 

 into the tube of the microscope like an ordinary objective, but the 

 one of 70 mm. here shown, is, by means of a conical adapter, 

 screwed into the ocular end of the tube, Fig. iSg. 



For illuminating the object, any suitable light may be used, 



but it is recommended that the light be concentrated by means 



of a bull's eye or some form of combination like the engraving 



glass, and that the condenser be so placed that it focuses the light tipon the objective, 



not upon the object. The object is then illuminated with a converging cone of light. 



§ 351. Record of Negatives. — As indicated in § 341-343 each 

 negative should have a record, see record blank on p. 219. On the 

 negative itself should be also written the main facts with carbon ink. 

 The name and magnification, date and any other details which may be 

 thought desirable can be put on the envelope containing the negative, 

 and then the negative stored like a catalog card as described above 

 (§ 343)- 



PHOTOGRAPHING LARGE TRANSPARENT OBJECTS 



§ 352. There are many large transparent objects which it is de- 

 sirable to photograph, e. g., chick embryos mounted whole, large sec- 

 tions of organs like the brain, etc. These must be photographed at a 

 low magnification. 



