ZOOLOGY AND BOTANY, MICROSCOPY, ETC, 
589 
difficulties arising from image-reversal are avoided. The lid of the bos 
is constructed with flaps which, when folded back, form supports for the 
hands of the operator. The front lets down, and thus light is admitted 
to the mirror. Lenses of 20, 30, and 50 linear magnification are supplied. 
Fig. 103. 
The stand is fitted with a micrometer-screw, and the general arrange- 
ment will be readily understood from fig. 103. 
A large size model of this instrument is also made with magnification 
up to 100 linear, with tooth-and-rack adjustment, and with plane and 
concave mirror. 
(3) Illuminating- and other Apparatus. 
New Apparatus for Application of Electric Currents to Living 
Microscopic Objects.* — Dr. Alfred Schaper describes the apparatus 
constructed to his designs by the firm of Zimmermann, Leipsic. His 
especial object was to secure that the object-holder should be free from 
polarising currents. He uses a piece of plate glass 12 by 7 cm., per- 
forated at the centre with a circular hole 20 mm. in diameter. Along 
each of the narrow sides is cemented a strong nickelled metal plate 
6 by 3 cm., furnished with binding screws as shown in fig. 104. This 
plate, which he calls the conductor, is placed on the object-stage so that 
the hole is immediately over the Abbe condenser. 
The object-holder varies according to the kind of experiment and 
the nature and size of the object ; but its general construction is such as 
to ensure communication of the current from the pole-plates. For 
this purpose both ends of the object-holder are mounted with a clamp- 
like metal piece which surrounds the edges of the holder and firmly 
unites its broad lower plane to its narrow upper one (figs. 105, 106, m). 
* Zeitschr. f wiss. Mikr., xiv. (1898) pp. 436-41 (5 figs.). 
