ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 701 



of correspondingly large dimensions. The underside of the stand 

 resembles Zeiss' binocular preparation Microscope. The mirror is 

 plane one side, concave the other, 7 cm. diameter, and has universal 

 movement. Over it there extends a frame : this can be placed upon 

 a sheet of white paper for affording diffused illumination. By means 

 of the frame black paper diaphragms can be fastened over the mirror, 

 if required, for stopping down the light-cone. The 10 by 10 cm. stage 

 has an aperture of 4 cm., which can be reduced to 2 cm. by a diaphragm. 

 Under the stage is a rotatory disk half -black, half -white, so that, if one 

 is working with reflected light, a black or a white background can be 

 had, as desired. The rotation axis of the disk which, in the binocular 

 stand is placed on the right, is here placed on the left, so as to leave 

 the right side quite clear for the drawing-paper. The entire upper part 

 of the stand is fastened by two screws to the lower part. The bent 

 arm bearing the optical system can be moved vertically up and down in 

 two different ways : first, in the ordinary way by rack-and-pinion ; 

 secondly, by push-movement in a swallow-tailed groove. A screw pro- 

 vided with a short lever clamps the arm in the groove. The second 

 movement is intended to lengthen the rack-range and to increase the 

 object distance beyond 10 cm. The reversal system is in a drum with 

 two tube-unions ; the upper one bears an ordinary Microscope ocular ; 

 the lower has the English objective thread and can take either a 

 revolver or a single objective. The construction is so arranged that 

 the tube-length without the revolver is 145 mm. ; with it, 160 mm., 

 so that even medium-power objectives can be used with the stand. An 

 extension ring of 15 mm. length allows of stronger systems to be used 

 even without the revolver. The author gives full details of objectives 

 and oculars. 



Ortner's Pocket-Loup.* — This instrument (fig. 105) is fitted with 

 two lenses ; one, an aplanatic, has a magnification of twenty ; the 



Fig. 105. 



other, an achromatic, has a magnification of ten, the combination giving 

 a magnification of 30 diameters. By pressing the projection or handle 

 to the right the aplanat only comes out, while by pressing it to the left 

 both loups are simultaneously extruded from the mount, and by a 

 special contrivance are accurately centred. 



Ortner's Loup-Stand.f — -This loup-stand or lens-holder (fig.;106) 

 which is chiefly intended for the use of entomologists, consists of a firm 



* Ortner's Katalog No. 7 (Entomologie), 1904, p. 42. 

 t Tom. cit., p. 44. 



