200 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



way. Illumination of the preparation is effected by a weakly convex 

 lens scre^Yed on above the polarizer : a lens system for convergent light 

 can also be applied if desired. The tube has the well-known arrange-" 

 ment of modern mineralogical Microscopes. As with the theodolite 

 method, strong magnifications are unnecessary ; a well cut rack-and- 

 pinion serves for both coarse- and fine-adjustments. The ocular end is, 

 at Wright's suggestion, equipped with an arrangement for inserting 

 micrometers, co-ordinate nets, gypsum plates, and so forth. 



Home-made Water Microscope.* — A. Tchikin describes how a really 

 efficient and powerful Microscope can be made in which the lenses are 

 constituted by drops of water. A thin (h mm.) zinc sector is pierced 

 with small accurately round holes, from '^ mm. to 1 mm. (fig. 12). In 





B AC K VI ew 



the centre C of the arch AB, on which is placed the holes, there is joined 

 a movable hand, or strip of hard tin-plate, about 2 cm. wide. The 

 sector and the hand are screwed together between two wooden blocks. A 

 ^-cm. hole E is drilled on the movable end of the hand, the l|-mm. wider 

 margins of the hand being bent to form a groove, or faucet, in which 

 may be placed a square piece of glass for a micro-object. Against the 

 hole is soldered to the hand a cylindrical diaphragm, i.e. a small brass 

 tube (about 1 in.), with zinc bottom, through which a small hole F, 

 about 2 mm. diameter, is drilled. Adjustment for focusing is by a strip 

 of thick paper, or carbon, rolled on the hand, which is slightly curved. 

 This strip of paper rolls along the hand, and, therefore, moves the 

 hand to and from the sector. The author states that a fine truly 

 spherical drop of water on a 1-mm. hole forms an ideal lens, with a 

 sharply distinct and colourless image, the power being near 100. 



* English Mechanic, xcvii. (1913) p. 109 (3 figs.). 



