ZOOLOGY AND HOTANY, MICROSCOPY. ETC. 791 



with concentrated nitric acid. Attempts to colour the different oxides 

 by the action of f'erro- and ferri-cyanide of potassium were unsuccessful. 



Mounting' of Specimens.* — R. Baumann describes some useful con- 

 trivances, which do not appear to be generally known, for mounting 

 polished sections. Small objects may be placed within a turned metal 

 ring on a level surface, with the polished surface down, and a slide on 

 which is a piece of modelling-wax, pressed down on the specimen. Two 

 pairs of rings, diameter 25 and 50 mm., height 15 and 25 mm., used 

 singly or in combination, give six variations of the arrangement for 

 objects of different size. Mounted in this way, the specimen may be 

 held by means of the stage clamps on the stage of a horizontal Micro- 

 scope. R. AVinkel's apparatus for marking a particular field is useful. 

 Screwed into the tube in place of the objective, it scratches a circle on 

 the polished section by means of a diamond point. Specimens too heavy 

 for observation with a horizontal Microscope when mounted as above, 

 may be mounted in a similar way, but with the polished surface at right 

 angles to the slide, and are then supported on a supplementary stage pro- 

 jecting (horizontally) at right angles from the ordinary stage. For large 

 and heavy objects the Microscope must be so constructed that it can be 

 placed on the object. The Zeiss I C stand permits of the replacement of 

 the foot and substage by a foot-plate, through an opening in which the 

 specimen is observed. For photography, a reflecting prism is fixed above 

 the eye-piece. 



Magnetic Properties in relation to Mechanical Tests.f — A. 

 Grriinhut and J. Wahn report on von Hoor's proposal to utilise the 

 magnetic and electric properties of materials to determine the mechanical 

 properties. Magnetism appears to be definitely related to almost all 

 physical phenomena, to mechanical stresses of all kinds, as well as to 

 influences of temperature, chemical composition, and structure. The 

 inter-relation between these phenomena is not sufficiently uniform, how- 

 ever, to allow of the determination of physical properties from magnetic 

 tests. 



Impact Tests. I — Gr. Charpy discusses the present position of the 

 impact bending test on notched bars, and concludes that this test 

 furnishes useful information which is not yielded by the tensile test. 



F. Schtile and E. Brunner§ have determined the volume of metal 

 strained beyond the yield point, in impact bending tests on notched 

 bars, and find that the influence of the depth of notch can be eliminated 

 by calculating the work done in fracture per unit of this volume. 



P. Breuil || states the conclusions he has drawn from a number of 

 impact tensile tests on plain bars. 



A. Leon and P. Ludwiklf find that the amounts of work done in 

 static bending and in dynamic bending are not in any uniform relation. 



* Metallurgie, vi. (1909) pp. 407-8 (8 figs.). 

 t Proc. Int. Assoc, for Testing Materials, No. 6 (1909) 5 pp. 

 X Op. cit., No. 7 (1909) 20 pp. (Official Report on Impact Tests of Metals, 

 submitted to the Copenhagen Congress, September 1909.) 

 § Op. cit., No. 6 (1909) 6 pp. (3 figs.). 

 || Op. cit., No. 10 (1909) 2 pp. f Tom. cit., 2 pp. 



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