ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



813 



passing the diai)liragm from right to left a beautiful scries of the most 

 brilliant tints was seeu — a fine navy blue changing to purple, orange, and 

 then to lemon-yellow, and lastly pale straw colour. A section ©f fortifica- 

 tion agate was taken which showed a small crystal of pure quartz in one 

 portion. With the diaphragm used as before from right to left, the colour 



Fig. 224. 



of the crystal was merged from bright-green to magenta, and then to a 

 velvety brown-red. With the usual revolution of the stage the colours 

 exhibited were green fading to a dull black. 



With this apparatus there is not only a more varied and brilliant series 

 of colours, but also a marked intensification of points of structure. In the 

 two above-mentioned slides delicate lines of crystallization were shown 

 which vv^ere invisible under ordinary circumstances. 



One of the small, curiously-branched bones of the red-horse, a fish 

 common in this region, was examined, and showed the bone-cells in a 

 remarkably distinct way, they being quite indistinct without the 

 diaphragm." 



Auer's Incandescent Gas-burner as a Microscope Lamp.* — Dr. K. 

 Biirkner recommends Auer's gas-lamp for use with the Microscope. He has 

 employed it for some time and finds it very satisfactory both in power 

 and quality. The light emitted is intense, but not blinding, and is rela- 

 tively white as compared with the ordinary gas-flame or that from parafiin. 

 Another advantage is the small amount of heat given off. The lamp is 

 merely an ordinary Bunsen's burner, the flame of which is surrounded by 

 a chimney or sheath impregnated with the nitrates of cerium, didymium, 

 lanthanum, ittrium. The incandescent chimney is upheld by a platinum 

 wire tied to a bearer which can be raised or lowered by means of a 

 screw, and is further inclosed in a glass chimney. As the incandescent 

 chimney consists of ash, it is necessarily somewhat susceptible of damage. 



1887. 



* Zeitschr, f. Wiss. Mikr., iv. (1887) pp. 35-8 (1 fig.). 



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