25 ) SUMMARY OF CURRENT RESEARCHES RELATING TO 
tlie author by A. Fromme, of Vienna, is represented in half its natural 
s : ze in fig. 26. The metal upright g is at its lower end / bent at a 
right angle, and attached to the horse-shoe foot of the Microscope & by a 
slide arrangement so that it can be easily removed or replaced at will. 
The horizontal arm i, at the upper end of the rod g , carries two vertiqal 
projecting pieces c, which fit into corresponding slots made in the 
fastening of the analyser. The latter, which is simply placed above the 
eye-piece, therefore remains fixed when the body-tube of the Microscope 
is rotated. The upright g is so far from the stage that the upper part 
of the Microscope never comes in contact with it during a complete 
rotation. 
If an analysing eye-piece is used instead of the simple analyser, its 
fastening must be provided with slots in which the projecting edges c fit 
as before. The length of the rod g is chosen to correspond to a tube- 
length of 16 cm. The draw-tube of the Microscope must be used in 
order to effect the exact adjustment of the arm i. The latter can, how- 
ever, be rotated about the horizontal axis e so as to give play for the 
slow motion. A rotation of this arm about a 
vertical axis is also possible. 
For most histological purposes observation 
of the behaviour of the preparation between 
crossed nicols is all that is required; but, 
where necessary, an arrangement can be easily 
added to the apparatus by which angles of ex- 
tinction, &c., can be measured. For this pur- 
pose cross-wires are fitted in the compensating 
eye-piece and a circle a divided in degrees and 
half degrees is clamped to the body-tube of 
the Microscope by the screw h. The scale 
thus turns with the body-tube while the eye- 
piece and analyser remain fixed. A projecting 
pointer b on the arm i serves as index for 
reading the angle of rotation. It is movable 
about a horizontal axis near the screw-head of 
the rod g so as to accommodate itself to the 
movement of the micrometer screw and re- 
main constantly in contact with the divided 
circle. 
In conclusion, the author gives some of his 
experiences with doubly refracting objectives 
and condensers. Of a series of new objectives 
few were found which were quite free from 
double refraction ; but in most cases it was 
so slight that it could only be recognized by 
special means. Apochromatics were found to 
have this fault more than ordinary achromatic 
objectives. 
New Microscope-Shade.* — Herr P. Schief- 
ferdecker has devised a new shade for the Microscope for which he 
claims many advantages. It lias the form represented in fig. 27, and 
* Z< itschr f. wiss. Mikr., ix. (1892) pp. 180-1. 
