ZOOLOGY AND BOTANY, MICEOSCOPY, ETC. 



359 



luminant, the author uses a nickelled iron reflector with incandescent 

 burner and condenser lenses, whose light he uses direct for downward 

 photography, but employs a hollow mirror for upward work. In order 

 to avoid the inconvenience which may arise from halation, the author 

 puts his plates into the dark slide with their glass side towards the 

 objective. 



(5)T«Microscopical Optics and Manipulation. ■] 



Engelmann's Microspectralphotometer with Grating Spectrum.* — 

 H. Siedentopf describes how the Thorp collodion grating has been 

 adapted by Messrs. Zeiss to Engelmann's instrument. 



Fig. 71. 



Fig. 71 shows the photometer two-thirds of its natural size. On 

 the frame containing the slit the upper part is secured by the clamp- 



* S.B. k. preuss. Akad. Wiss. zu Berlin, xxxi. ii. iii. (1902) pp. 706-10 (3 figs.)- 



