582 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



Fig. 111. 



(3) Illuminating- and other Apparatus. 



New Arrangement for Viewing Diffraction Spectra.* — Mr. J. 

 Rheinberg finds that the best method of viewing diffraction spectra is 

 to mount in a short tube the objective of one of the 7s. 6d. toy Micro- 

 scopes, which is in effect a lens of about 

 [ in. focus stopped down to an actual 

 aperture of about 1 mm. This diffraction 

 ocular, as it may be called, shows the 

 spectra splendidly, magnifying them at 

 the 'same time. It gives plenty of light, 

 and the spectra cannot shift. Fig. Ill 

 clearly shows the arrangement. A is the 

 ocular fitting on to the top of B, the usual 

 eye-piece. The sliding collar s allows of 

 adjustment to any power eye-piece. The 

 spectra viewed in this way are not those 

 formed at the back of the objective, but 

 those re-formed above the eye-piece. 



Sanger, Shepherd, & Co.'s Improved 

 Optical Lantern. — Fig. 112 shows a lan- 

 tern of the highest class especially suited 

 to the requirements of a scientist. The 

 whole of the framework is extremely rigid. 

 The lantern body is entirely constructed of metal truly finished to 

 gauge ; the stage for jet or arc lamp fits the body accurately, and is 

 provided with every adjustment. The optical base consists of a series 

 of stout truly-fitted brass tubes, all of which, with the exception of the 



Fig. 112. 



rear pair, are entirely removable. The condensers are fitted in bayonet- 

 clutch cells ; they can be instantly changed, and are carried by a plate 

 litted to the large stout cast-brass uprights. The slide stage is carried 



* Journ. Quek. Mier. Club, 1901, pp. 63-4 (1 fig.). 



