ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
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silk and spider threads are thus overcome, and the quartz, while equalling 
these other materials in fineness, surpasses them in strength. Mr. Wads- 
worth asserts that anybody, after a little practice, can easily make the 
fibres, the only essential apparatus being an oxyhydrogen blow-pipe 
which must be fed by compressed oxygen and fairly pure hydrogen (coal 
gas is unsatisfactory). He has found no method for “ shooting” the fibres 
superior to the bow and arrow method first used by Prof. Boys. Previous 
to immersion in the silvering solution, the fibres should be chemically 
cleaned by successive immersions in (1) strong nitric acid ; (2) distilled 
water ; (3) strong caustic potash ; (4) distilled water. He finds it con- 
venient to mount a dozen fibres in a glass rod frame, fastening them 
with fused shellac which resists both hot acid and hot alkali. The frame 
can then he laid aside and the fibres removed for use when required. 
Novelties in Polarisation Apparatus.* — W. Wicke classifies sac- 
oharimeters into: — (1) Apparatus for circular polarisation requiring 
under all circumstances homogeneous illumination — usually sodium 
light ; and (2) apparatus with wedge compensation and linear scales 
which can be used with white light. 
(1) This includes the old forms of: — Mitscherlich, Wild, Halb- 
Fig. 30. 
schatten-Laurent, and Lippich. The best is that of Lippich, which 
excels in accuracy and certainty; its advantage depending upon a 
tripartition of the field of view. 
(2) This includes Soleil’s saccharimeter depending on a now 
antiquated colour system, with the improvements by Yentzke and by 
Scheibler, as well as applications of the half shadow ( Halbschatten ) 
system. Soleil, although still much used, is unsatisfactory, both in 
* Berichte der Deut. Pharm. Gesells., 1898, pp. 7-15 (7 figs.). 
