ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



453 



difficulties ill the way of construcbiag a pactical apparatus and keeping 

 tie camera within portable liuiits. The paper deals with the nature of 

 the various optical and other problems involved, and shows how they 



Optical system 



Focusing screen 



Jlovenient rotating 

 the optical system 



Lateral micrometer 

 movement 



Pig. 83. — Section of micro-spectra camera. 



have been solved. Figs. 83 and H4 show a sectional plan of the camera 

 and a section of the optical system, a peculiar feature of the latter being 

 a compound prism (which was specially computed for Rheinberg by 

 Conrady) to produce a spectrum in which the colours are evenly dis- 



FiG. 84. — Section of optical system. 



A, Zeiss 75 mm., raicro-planar objective on focusing mount. 

 B, Spectacle -prism. C, Field-lens. D, Line-screen or 

 grating in adjustable frame. E, 75-mm. micro-planar 

 objective. F. Compound prism. G, Cylinder spectacle- 

 lens, 120-in. focus. 



tributed as in a grating spectrum, thus obviating the crowding of the 

 red end of the spectrum and undue extension of the blue end incidental 

 to the usual spectra produced by prisms. 



The ordinary and best way of viewing the pictures is to inspect 

 them on the focusing screen ; for this a strong artificial illuminant is 

 needed. Another way is to view them on the line screen by means of 

 an eye-piece, substituted in place of the objective of the camera ; for 

 this, daylight or any weak illuminant suffices. They may also be pro- 

 jected in a size of 3-4 ft. diameter on a lantern-screen. All these ways 

 have been publicly demonstrated, and are reported to have given results 

 absolutely faithful as regards clour rendering, together with exceptionally 

 tine rendering of the characteristic sheen and texture of metals, silk, 

 porcelain, etc. 



The camera can be used in conjunction with the Microscope for 

 photomicrography (tig. 85). In that case the first objective is removed, 

 imt oqe of the field lenses is left in position. The Microscope attach- 

 ment is then screwed on in place of the objective. This attachment 

 consists essentially of two sliding-tubes (one of which is scaled), in 

 which the eye-piece of the Microscope can be inserted. To secure proper 



