ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



743 



moulds replace separate pieces screwed together. Thus the foot and pillar 

 and the stage and limb are both cast in one solid piece. The two pieces 

 are connected by a strong knuckle joint, upon which the instrument is 

 inclinable to the horizontal. As far as the stand is concerned, there is 



Fig. 16?.. 



no difference between the Praxis (fig. 161) and Bactil (fig. 162) models. 

 The important feature of the latter is a new form of mechanical stage, 

 which has a travel of 2 in. horizontally and H in. vertically. The 

 horizontal movement (fig. 168) can be removed by unscrewing two 



Fig. 164. 



thumb-screws, leaving the surface of the stage 3| in. square, as shown in 

 fig. 16-4. The compound substage is fitted with focusing rackwork and 

 centring screws, and can be turned out of the optic axis when desired. 

 Other accessories supplied are a coned iris diaphragm and a spiral 

 focusing screw with Scop condenser in lieu of the one previously 

 described. 



Beck's " Imperial " Metallurgical Microscope. — This Microscope 

 (fig. 165) is a modification of the Imperial Microscope, specially made 

 for metallurgical purposes, in which the large concentric rotating stage is 

 replaced by a square mechanical stage, the whole of the stage and sub- 



