ZOOLOGY AND BOTANY, MICIIOSCOPY, ETC. 451 



Microscope stage, and the position of any desired point in the prepara- 

 tion may be recorded by noting the latitude and longitude, so to speak, 

 of the two upper corners of the slide. 



Maey, E. — Die raumliche Lagerung von Kanten im Mikroskopischen Objekt bei 

 Dunkelfeldbeleuchtung. 



Zeitschr. wiss. Mikrosk., xxis. (1912) pp. 48-57 (5 figs.). 



SiEDBNTOPF, H. — IJber ultramikroskopische Abbildung linearer Objekte. 



Zeitschr. wiss. Mikrosk., xxix. (1912) pp. 1-47 (22 figs.). 



(.4) Photomicrography. 



Micro-spectra Method of Colour Photography. — A method of colour 

 photography, by purely optical means, involving but a single exposure 

 on a single plate, and dispensing with the aid of artificial dyes or 

 colouring matter, was suggested by Julius Rheinberg in 1904,* and has 

 since that time been worked out and brought to a high state of per- 

 fection by the latter and his brother, Ernest Rheinberg. It forms the 

 subject of an exhaustive paper in the Journal of the Royal Photographic 

 Society, and elsewhere.t 



The process necessitates a camera of complicated construction 

 (fig. 81), but, given the camera, is very simple to work, the methods 

 being those employed in ordinary black and white photography. A 



Fig. 81. — Micro-spectra camera on stand. 



black and white negative is taken in the camera on a panchromatic 

 plate ; a lantern slide is made from it and placed in the camera in . the 

 position previously occupied by the negative. White light is projected 

 through the apparatus, and the picture, after slight adjustments, flashes 

 out in its true colours. 



The general theory of the process consists in producing by optical 

 means a surface composed of hundreds of complete but very narrow 

 spectra, lying next to one another, the spectra being so close together 

 as to render the individual colours indistinguishable to the unaided eye, 

 so that the surface appears to l)e white. The photographic positive is 



* British Journ. Photography, Jan. 1, 1904. 



+ Journ. Roy. Photog. Soc, April, 1912; Nature, May 23, 1912. See also 

 British Journ. Photography, Colour Supp , May, 1912, and following months. 



