APPLICATION OF PHOTOGRAPHY. 



157 



tionate to the distance. On this screen is placed a sheet 

 of photogenic paper intended to receive the magnified 

 picture. We ought to add, however, that it requires con- 

 siderable practice to avoid the distortion and error of 

 definition occasioned by a want of coincidence in the 

 chemical and visual foci. Imperfections are much in- 

 creased when the highest powers of the microscope are 

 employed ; false notions of structure are also given, 

 which is the case in Mr. Wenham's photograph of P. An- 

 gulatum. 



Mr. S. Highley has a mode of adapting an object-glass to 

 the ordinary camera, for the purpose of taking microscopic 

 objects on collodion and other surfaces, fig. 96; a sec- 

 tional view of his arrangement is here given, which is 



in HI ST'— 



Fig. 96. — Highley' s Camera. 



very compact, steady, and ever ready for immediate use. 

 The tube a screws into the flange of a camera which has 

 a range of twenty-four inches; the front of this tube is 

 closed, and into it screws the object-glass B. Over a slides 

 another tube c; this is closed by a plate, D, which extends 

 beyond the upper and lower circumference of c, and carries 

 a small tube, e, on which the mirror f is adjusted. To the 

 upper part of d the fine adjustment G is attached ; this 

 consists of a spring-wire coil acting on an inner tube, to 

 which the stage-plate h is fixed, and is regulated by a gra- 

 duated head, k, acting on a fine screw, likewise attached to 



