362 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



of the lenses are not convenient for ordinary stands, and the author, 

 therefore, proposes the modified design shown in fig. 44. The tube T 

 is provided with a sufficiently long draw-out tube A, worked by rack-and- 

 pinion. At the lower end of the whole tube is the reversed objective 

 \o~bj. 1) and at the lower end of the draw-out the ordinary objective 

 (ply. 2). The draw-out must be of such a length that the objective at 

 its lower end, when the tube is completely inserted, does not reach the 

 reversed objective. A further distinction from an ordinary stand is in 

 the action of the prismatic bar P which, by rack-and-pinion, may be 

 raised so as to bring the body to a greater height above the stage. The 

 attainment of this increased working space is also effected by making 

 the object stage adjustable in level. 



Brunnee's Polarisation-Microscope-Polymmeter.* — This instru- 

 ment of E. Brunnee's is distinguished from an ordinary mineralogical 

 Microscope only by the kind of fine-adjustment used. The micrometer- 

 screw is actuated by means of a drum applied to the tube, and in the 

 drum is a circular wedge of weak obliquity. The fine-adjustment of 

 the objective is attained through the sliding of a bar, connected with 

 the objective, along this wedge, so that a simultaneous rotation of the 

 objective takes place about the axis of the instrument during the fine- 

 adjustment. This mechanism facilitates at the same time a rotation of 

 the inner Nicol, which rotation is independent of the polariser, but can 

 also engage with it by means of a toothed wheel over-movement. 



Rinne, P.— Le Microscope polarisant, trad, par L. Pervinguiere, avec preface par 

 A. de Lapparent. Paris, 1904, 160 pp. 



(2) Eye-pieces and Objectives. 



New Form of Ehrlich Eye-piece for Counting Blood-corpuscles. — 

 This apparatus, made by E. & J. Beck (fig. 45), is a Huyghenian eye- 

 piece of the No. 1 E.M.S. standard size. 

 It fits this firm's " London " Microscopes 

 and those of Continental makers. It is 

 provided with an adjustable square aper- 

 ture, the size of which can be varied from 

 1 mm. to 8 mm, so that it can be easily set 

 for any desired size. 



The actual area to which the size in use 

 corresponds w T ith any particular object- 

 glass can be ascertained by slipping a stage 

 micrometer on the stage of the Microscope. 



Fig. 45. Magnifying Power of Microscopical 



Objectives. f — L. Malassez points out that 

 there is no precise definition of the phrase "magnifying power." 

 He suggests that it would be advantageous to express the magni- 

 fying effect of a lens in terms of unit distance from its posterior 

 face, and that the term "magnifying power" could be conveniently 



* Zentralbl. Mm. Geol. Palaont., 1905, pp. 593-5 (1 fig.), 

 wiss. Mikrosk., xxii. (1905) pp. 586-7. 



f Comptes Rendus, cxli. (1905) pp. 880-1. 



See also Zeitschr. 



