126 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



Fig. 18. 



facilitating the changing of the diaphragms. The carrier is arranged 

 to hold either a series of graduated apertures alone or in combination 



with a series of central 

 stops, and a few dia- 

 phragms are supplied of 

 special forms, such as 

 single or double slots, 

 and single or double 

 circles cut more or less 

 eccentrically, so that a 

 great variety of dif- 

 ferent kinds of illumi- 

 nation can be obtained. 

 We understand that 

 the sliding arrangement 

 of the tube supporting 

 the diaphragm-carrier, 

 as shown in the figure, 

 was suggested by Dr. 

 Dallinger as being more 

 convenient in use than 

 the system first em- 

 ployed by Messrs. 

 Powell and Lealand, in 

 which the tube was 

 wholly removed for 

 every change in the dia- 

 phragms. 



Koch and Max Wolz's Lamp. — Fig. 18 shows this lamp in position, 

 when the solid glass rod is used to illuminate a transparent object. The 

 principles of its construction were described at 

 p. 1025 of the last volume of this Journal. 



L is the source of light — a mineral oil lamp. 

 Outside the glass chimney is a black one, on the 

 inside of which is a reflector E. At O is an opening 

 fitted with a short tube, in which is fixed the curved 

 glass rod G. The end of this rod is squared off, and 

 lies underneath the stage. The quality of the light 

 may be modified by putting coloured glasses upon 

 the smooth end of the rod. 



Although the source of light shown in the illus- 

 tration is derived from mineral oil, gaslight or 

 other sources can be used.* 



Adjustable Hemispherical Illuminator. — The 

 Bausch & Lomb Optical Co. now fit this illuminator 

 as shown in fig. 19. The glass hemisphere is 

 attached to an adjustable rod which slides in an 

 adapter screwing on a suhstage adapter. It is a 

 very convenient accessory in instruments having 

 separate mirror and suhstage bars, as any number 



* Cf. Zeitsclir. f. Wiss. Mikr., v. 

 p. 1025. 



(1888) p. 478 (1 fig.); and this Journal, 1888, 



