493 



surface, then polished on a series of emery papers of increasing 

 fineness — usually attached to a disc rotated by an electric motor. 

 The final polish was given by a cloth-wheel charged with ordinary 



jewellers* rouge. This method will give a sufficiently high polish 

 as to eliminate all scratches under all but the highest power.-. 

 After polishing a section, it should always be examined before 

 etching for blow-holes, etc., due to foreign matter entangled in 

 the metal. A photomicrograph taken at x 100 was .shown on the 

 screen of a polished surface of steel, in which was a thread of slag 

 showing >lack line on the white ground of the polished metal. 



Another photograph showed the presence of two kinds of slag, 

 one darker than the other. The line of slag indicates the direction 

 in which tin- steel has been rolled. If a surface is polished with 

 soft material, the .harder constituent will stand out in relief 

 above the softer one. A number of very interesting slides taken 

 by the Autochrome process were shown, well exhibiting the 

 colours of the >■ Qstituents brought out by heat-tintingr. 



On April 3rd, the Quekett Microscopical Club commenced their 

 Saturday afternoon excursions for the season, visiting, by kind 

 permission of the secretary of the Royal Botanic Society, the 

 Botanical Gardens, Regent's Park. The attendance, though not 

 a record, was good, thirty-five members taking advantage of the 

 fine afternoon. Notwithstanding the late spring and recent 

 cold weather, the water of the lake yielded abundance of micro- 

 scopic life. Free-swimming Rotifera were particularly plentiful, 

 both in species and numbers. Pterodina and many species of 

 Brachionus were made out. Several members, before leaving, 

 iinnounced the capture of Melicerta, and one believed he had 

 acquired Fredericella. Infusoria were plentiful, among them 

 Stentor. Several Hydras were recorded, and the usual Ento- 

 mostraca (Chydorus, etc.), with some of the Nauplius forms. 

 Among Algae, two species of Closterium were recognised, and, 

 on plant-pots in one of the conservatories, Symploca, and a fine 

 example of Chroococcaceae. 



