ZOOLOGY AND BOTANY, MICROSCOPY. ETC. 



9 



year's trial. The designer's object was to contrive an apparatus which 

 should possess the universal applicability and essential advantages of 

 large, and correspondingly expensive Microscopes, without exceeding the 

 cost of small cheap instruments. The ordinary rack-and-pinion move- 

 ment was used for the coarse-adjustment ; but for the fine-adjustment 

 a simple solid slide-movement was constructed (fig. 8). The slide S 

 is applied immediately behind the guide-piece of the coarse adjustment 

 Z, and is pressed against the micrometer screw M by means of the 

 spring F. The efficiency of the micrometer screw-action on the move- 

 able part is secured by the point-contact between the micrometer screwtip 

 and the hardened steel plate K, the result being a clean regular movement 

 and the elimination of all dead-way in either forward or back screwing. 

 The micrometer screw is set obliquely with regard to the guide-piece, 



Fig. 8. 



partly on account of the proximity of the slide-movement and coarse- 

 adjustment, and partly to facilitate manipulation. This position does 

 not prejudice in the least the delicacy and trustworthiness of the action. 

 The whole arrangement is enclosed within the tube-holder, and thereby 

 completely protected from dust. The large Zeiss* model (i") and 

 Reichert's large new Microscopes have lateral micrometer screws, the 

 essential advantage derived being that the upper part of the stand is 

 independent of the fine adjustment mechanism, and can therefore be 

 given a considerable projection. But owing to the complexity of the 

 technical details, the method is costly, and only applicable to expensive 

 Microscopes. The author points out that his simplified construction of 

 the slide-movement accompHshes the same advantage at slight cost. 

 The upper part of the hmb projects considerably (fig. 9), and is shaped 

 for a massive hook-like handle. The stage which can, therefore, be of 

 large size, is prolonged into a broad continuation F reaching up to the 

 handle : the median diameter is 125 mm. The extent of the heavy 

 horseshoe foot is 143 mm. long by 113 mm. broad. The height of the 



* Cf. Berger's Microscope, see this Journal, 1898, pp. 583-7. 



