112 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



If the stain be on a weapon or piece of jewellery, it should first be 

 wetted with ammonium sulphide. A small portion may then be scraped 

 ■off with a knife and treated as above. 



In dealing with seminal stains the suspected stain is boiled for 

 2 minutes in an aqueous solution containing tannin h p.c and sulphuric 

 acid 1 per thousand. It is then washed for 2 minutes in a solution 

 made by adding 1 part of saturated ammonia solution to 400 of water. 

 This is followed by immersion for 5 minutes in a solution containing 

 1 in 10,000 potassium l)ichroniate and 1 in 1000 sulphuric acid. Next 

 it is transferred for 2 minutes to a 2 p.c. solution of potassium cyanide. 

 It is then rapidly washed in distilled water, scraped, and teased up on a 

 slide, dried, fixed by heat, and stained. 



Swift's Slitting and Polishing Machine for Rocks.* — This apparatus 

 (fig. 24) is practically self-acting when once the material to be cut has been 



i'lG. 21. 



placed in position. It is then only necessary to turn the handle, which 

 •carries either the slitter or the polishing lap. -The apparatus works at 

 considerable speed, which is effected by multiplying-gear fitted to the 

 vertical shaft to wliich the handle is fixed. The ordinary gut-band is 

 superseded by a fine endless chain, which is geared in such a way that it 

 cannot be deranged. A fine-adjustment is fitted to the clamp which 

 holds the sections, so that a specimen can be cut to any given thickness, 

 thus enabling the sections to be cut so thin that they require little or no 

 reducing upon the lap. The size of the apparatus is 24 in. by 12^ in. 



Metallography, etc. 



Liquid Crystals of Ammonium oleate.f — F. Wallerant describes 

 the peculiar optical properties of a layer of ammonium oleate compressed 

 between a shde and a cover-glass. Under the influence of vibration 

 portions of the turbid layer become transparent, then possessing a 

 definite crystalline orientation. Ammonium oleate may exist in four 

 polymorphic modifications. 



The Internal Architecture of Metals. | — A 'report of a popular 

 lecture by J. 0. Arnold at the Royal Institution. Some metallographic 



* Swift and Son's Catalogue, 1906, p. 28, fig. 26. 

 t Comptes Rendus, cxliii. (1906) pp. 694-5 (1 fig.). 

 X Nature, Ixxv. (1906) pp. 13-5 (3 figs.). 



