348 



SUMMARY OF CUKRENT RESEARCHES RELATING TO 



a nut at B to the curved lever C. The thread of the micrometer-screw 

 is 50 to the inch, and the ratio of the curved lever is 1 in 4. The small 

 wheel D is intended to minimise friction. The curvature of the lever 

 is so arranged as to ensure that D is lifted by an amount exactly equal 

 to the horizontal movement of B. A spring F on the guide-pillar E 

 keeps the wheel down to its work and causes the downward motion. 

 Each revolution of the milled heads corresponds to 0'125 mm., or a^otlis 

 of an inch. All slides are sprung and screwed. 



Williams' "Wonder" Microscope.* — This instrument (fig. 62), 

 though extremely cheap, is constructed on the lines of high-class models. 



It is intended for low powers, focusing 

 being effected by means of a rack-and- 

 piuion coarse-adjustment. A 1 or 2 in. 

 objective is supplied, and No. 2 eye-piece 

 and mahogany case. 



v33 Illuminating: and other Apparatus. 



Macro-projection by use of the Micro- 

 scope.f — F. K. Studnicka has been suc- 

 cessful, by a simple method, in obtaining 

 macro-projection and micro-projection by 

 use of the same Microscope. He inserts 

 the diapositive at a certain distance from 

 the lower lens of the Abbe condenser be- 

 longing to the Microscope in use. This 

 lens faces the light source, and the dia- 

 positive is placed in the optic axis l)e- 

 tween the Microscope and the large con- 

 denser of the projection apparatus. The diapositive in this position 

 yields a small delicate image on which the tube can be adjusted, and 

 which can be projected with the same accuracy as a microscopical 

 preparation. For perfect success much depends on the proper choice 

 of objective and ocular. The author selects his objective, which pro- 

 duces the minimum distortion in the image through the Abbe con- 

 denser and his weakest ocular. In his case these happen to be 

 Reichert's objective No. 2 and ocular No. 1. It is important to draw 

 out the tube, and as far as possible to disregard peripheral parts of the 

 image-field. The image of the diapositive is clear, and the only fault 

 to be found with it is that it is not perfectly flat. But this objection is 

 unimportant if one limits oneself to the centre of the field. The magni- 

 fication depends on the dist,auce of the diapositive from the Abbe con- 

 denser, and the holder must be pushed backwards or forwards on tlie 

 bench until the most favourable position has been secured. A simple 

 double fork is found to be a satisfactory form of holder. 



U V-Filter and U V-Filter-lamp as Aids in Luminiscence 

 Analysis. J — H. Lehmann describes the progress made in ultra-violet 



* Williams and Co.'s Special Catalogue, 1911. 



t Anatom. Anzeig., xl. (1912) pp. 662-4. 



X Zeitschr. f. Instrumentenk., xxxii. (1912) pp. 43-54 (6 figs.). 



Fig. 62. 



