ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 91 



MICROSCOPY. 



A. Instruments, Accessories, &c.* 

 Q) Stands. 



Swift's students' Petrological Microscope. f — This Microscope 

 (fig. 3) has recently been further improved from suggestions of J. S. Flett. 

 The coarse-adjustment is by means of patented spiral rack-and-pinion, 

 the slow focusing adjustment by a millimetre screw, the milled head 

 of which is divided to read to j^^ mm. The glass-covered revolving 

 stage has the edge divided to 360° reading to 5' by means of a vernier. 

 The polariser is fitted with divided flange and spring-catch to indicate 

 the crossing of the Xicol prisms and is made to throw out of the optic 

 axis when required ; immediately above the polariser is fitted the con- 

 vergent system of lenses. The analysing prism is fitted in a metal box 

 which slides into the optical tube ; below this is cut an opening for the 

 introduction of a quartz wedge, undulation plate, or gypsum plate. Above 

 the analysing prism is fitted a Bertrand lens with telescopic adjustment, 

 by means of which the interference figures are perfectly shown in thick 

 or thin crystals. The tube of the cross-webbed eye-piece is provided 

 with an opening to allow of the use of a quartz wedge or micrometer. 



Swift's University Binocular Microscope. | — This Microscope 

 (fig. 4) is of medium height, and is designed to meet the requirements of 

 the science student and of those who desire a binocular instrument for 

 scientific recreation. The coarse-adjustment is effected by Swift and 

 Son's patented spiral rack-and-pinion, and the slow movement by their 

 Climax fine-adjustment. The stage, 4|- in. by 3f in., will be found 

 useful for systematically working over a slide. The right-hand corner 

 of the main stage is divided into millimetres for the purpose of recording 

 the position of the object for future reference. On the under side of 

 the stage is a tube of the R.M.S. standard size for receiving apparatus. 



Draper's Improved Magnifier. § — This magnifier (fig. 5) designed by 

 D. Draper is intended for the examination of ores, rocks, and other solid 

 bodies. By means of a concave reflector attached to the magnifier light 

 can be concentrated on any portion of the object under examination, and 



* This subdivision contains (1) Stands ; (2) Eye-pieces and Objectives ; (3) 

 Illuminating a.nd other Apparatus; (1) Photomicrography; (5) Microscopical 

 Optics and ^Manipulation ; (6) Miscellaneous. 



t Swift and Son's Catalogue, 1906, p. 21, fig. 17. 



% Tom. cit., p. 11, fig. 8. § Tom. cit., p. 66, fig. 103. 



