244 



PHOTO-MICROGRAPH ) 



[C//. VIII 



berg, Francotte, Spitta an'd the special catalogs on photo-micrography and 

 projection issued'by the great opticians. The Journal of the Royal Micro- 

 scopical Society and of the Ouekett Micr. Club; Zeit. wiss. Mikroskopie; the 

 Trans. Amer. Micr. Soc.; the Amer. Monthly Micr. Journal; the Journal of 

 Applied Microscopy. 



For the photography of metallic surfaces, see the various journals of 

 engineering and; metallurgy, but especially Sauveur's journal, the Metallo- 

 graphist, begun in 1898; Jour. Roy. Micr. Soc. 



See the works on' photo-micrography and photography for the details of 

 lantern slide making. See for the Petri dishes and test-tubes, Atkinson, 

 Botanical Gazette, xviii (1893), p. 333; Spitta, Photo-Micrography (1899), P- 26. 



For photography with ultra-violet light see Zeiss special catalogs. Jour- 

 nal of the Royal Microscopical Society, Zeitschrift fur wiss. Mikroskopie; 

 Dr. August Kohler, Zeit. wiss. Mikr. Bd. xxi, 1904, pp. 129-165, 273-304; six 

 plates; Band 24, 1907, pp. 360-366. Dr. H. C. Ernst of the Harvard Medical 

 School; Jour. Med. Research N. S. Vol. 9, 1905-6 pp. 463-468, plates. 



4 3 C 



Various Spectra. These spectra illustrate some of the points in the dis- 

 cussion of color screens ( 291). 



The Solar spectrum shows that all the wave lengths of light are present 

 except for the very narrow dark lines (Fraunhofer lines, \ 214). 



The Sodium spectrum is an example of the spectrum of an incandescent 

 gas ; it is also an extreme example of monochromatic light. Sodium light is 

 very brilliant, but the appearance of surrounding objects gives one a good idea 

 of the changed appearance which the universe would assume if illuminated by 

 monochromatic light. 



The spectra of permanganate and methemoglobin illustrate well the ab- 

 sorption spectra of colored substances. 



If one were to use permanganate for a color screen the object photograph- 

 ing most successfully would be one transmitting light in the E region of the 

 spectrum. 



Methemoglobin would answer well as a color screen for an object trans- 

 mitting light at the violet end of the spectrum and between the lines DE. 



