ZOOLOGY AND EOTANY, MICROSCOPY, ETC. 741 



convex under side holding a drop of dilute sulphuric acid, the top some 

 drops of cold water ; after the reaction the cooling water is removed 

 and the underneath drop put upon a varnished glass or a polished 

 plate of barytes. Into the test-drop is put a little sodium chloride, 

 beautiful six-rayed rosettes of • 1 mm. form, then hexagonal plates 

 and prisms with pyramids. 



Silicon and Boron. — The following method allows of these two, 

 i. e. supposing both to bo present, to be separated and detected. The 

 test is treated in the platinum spoon with a mixture of sulphuric and 

 hydrofluoric acids, and beated very gently, silicon fluoride alone vola- 

 tilizes and is collected and tested as under Fluorine. After addition 

 of more hydrofluoric acid the heating is repeated but until fumes of 

 sulphuric acid escape. The drop on the platinum cover is then 

 evaporated to dryness at about 120°, the residue moistened after a 

 minute or two with a drop of water, the solution brought on to a 

 varnished glass, and a little potassium chloride added ; potassium boro- 

 fluoride separates in acute plates and rhombs, whose diameters are as 

 2 : 3, size 0-030-0 -050 mm., the obtuse angles are sometimes replaced 

 by edges. If no crystals separate at first, it is necessary for the drop 

 to evaporate to dryness before making a conclusion. 



Water is tested for by heating in a capillary tube as usual, with 

 due precautions. The delicacy of the reaction may be increased by 

 bringing into the tube a very little of the residue left by evaporating 

 an alcoholic solution of magenta on glass ; these thin skins are 

 opaque and have a beetle-green lustre, on becoming moist they appear 

 transparent and red. 



The author is still occupied with finding suitable tests for some 

 of the rarer elements, and with the more difficult task of finding 

 reactions capable of being carried out on the rock section itself. A 

 dozen examples are given of the applicability of the above methods ; 

 thus in - 2 mgr. of sodalite were detected aluminium, calcium, 

 potassium, and sodium, and in • 1 mgr., chlorine ; in * 2 mgr. axinite 

 were detected silicum, boron, aluminium, magnesium, and calcium ; 

 and in • 3 mgr. apophyllite containing 1 per cent, fluorine, the latter 

 was detected. 



Microscopical Characters of Hailstones.* — A hailstorm at Inns- 

 bruck in September 1881, afforded J. Blaas an opportunity of ex- 

 amining the hailstones and determining the following results amongst 

 others. 



The opaque white layers which occurred in alternation with 

 transparent ones and showed the appearance of radiating structure 

 owing to the radial arrangement of the air-bubbles, never afforded 

 any evidence that the crystalline elements were radiating in their 

 arrangement ; on the contrary, they were seen by the use of polarized 

 light to consist of granules of ice, quite irregular in shape. The 

 enclosed air-bubbles, some of which were of the smallest possible 

 dimensions, had very irregular lobate forms, which always showed a 



* Bote f. Tirol u. Vorarlberg, 1881, No. 215. Cf. Naturforsclier, xiv. (1881) 

 p. 454. 



