ZOOLOGY AND BOTANY, MICROSCOPY. ETC. 



719 



as above, but by application of suitable objectives and oculars, may also 

 be used as a reading Microscope for general laboratory use. 



Fab be, Ch. — Les nouveaux microscopes. 



[Gives some account of recent progress in the manufacture of instruments.] 

 Memoirs de VAcad. des Sci. de Toulouse, v. (1905) pp. 289-96. 

 Plate, L— Demonstration eines Schau-Mikroskopes fur bffentliche Museen. 



Compt. Rend, des Seances du Conyres intemat. de Zool. Berne, 1904. 



Basle, 1905, pp. 529-30 (1 fig.). 



(3) Illuminating- and other Apparatus. 



Watson's Ball-bearing Sliding Bar.— Tbe illustration (fig. 7'.)) shows 

 the method by which this sliding bar is adapted to the stages in Watson 

 and Sons' Microscopes. A grooved edge is provided in the stage, and 



Fig. 79. 



two steel balls fit into the grooves and are maintained in position by a 

 light spring pressing on the back. A very soft movement is obtained 

 by this means. 



Simple. Photometer.* — Stolze suggests the use of two right-angled 

 prisms, cde, and cfg, ug. 80, fastened to a thin sheet of opal glass. 



Assuming the light sources to be at a and b, the prisms have only 

 to be shifted to]the right or left till the illumination is even, and the 



' — K^~' 



Fig. 80. 



distances a c and b c measured ; then the intensities of the lights will 

 be as (acf : (be) 2 . This arrangement can obviously also be used to 

 compare the actinic power of the two lights, and would be useful in 

 measuring the power of the various illuminants for the Microscope. 



Tswett's Luminoscope.f — M. Tswett, in discussing the interest 

 universally excited by ultramicroscopes, draws attention to his lumino- 



* Brit. Journ. Photography. See also English Mechanic, lxxxiv. (1906) p. 299 

 (1 fig.). 



t Tswett, Zur Ultramikroscopie, Ber. Deutsch. Bot. Gesell., xxiv. (1906) p. 234. 

 See also Zeitschr. wiss. Mikrosk., xxiii. (1906) p. 199. 



8 B 2 



