496 



SUMMARY OF OUBRENT RESEARCHES RELATING TO 



MICROSCOPY, 

 a. Instruments, Accessories, &c.* 



Viallanes' Photographic Microscope— Compound Images by the 

 Method of Successive Exposures.! — At the outset of an inquiry into 

 the best methods and conditions of micro-photography, Dr. H. 

 Viallanes premises that those instruments, in which the dark chamber 

 is fixed directly to the tube of the instrument are subject to a serious 

 defect, both because the weight of the chamber must affect the micro- 



FiG. 82. 



metric screw, and also because the tremors caused by inserting and 

 removing the negative are communicated to the instrument, and may 

 displace the object and with it the photographic image. It is a 



* This subdivision contains (1) Stands; (2) Eye-pieces and Objectives; 

 (3) niuminating Apparatus; (4) Other Accessories; (5) Photo-micrography; 

 (6) Manipulation ; (7) Microscopical Optics, Books, and Miscellaneous matters. 



t Viallanes, H., ' La Photographic appliquee aux Etudes d'Anatomie Micro- 

 scopique,' 63 pp. and 4 figs. (8vo, Paris, 1886). 



