ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
669 
special arrangement for the simultaneous rotation of the two nicols. 
This construction is obviously borrowed from the Dick Microscope as 
made by Mr. Swift, and described in this Journal, 1889, p. 432. The 
Fig. 72. 
Microscope is particularly suitable for the observation of glowing 
minerals in polarized light. 
Combination of Microscope and Reflecting Goniometer.* — Prof. 
A. Schrauf describes a combination of Microscope and goniometer 
which is useful for the measurement of minute crystals ; the ordinary 
telescope of the goniometer fails to give sufficient magnifying and de- 
fining power to enable the edges of very small crystals to be properly 
centered and adjusted. For the measurement of such crystals he proposes 
to add to the ordinary instrument a Microscope directed vertically with 
its line of sight passing through the axis of the goniometer. Since the 
collimator and telescope are inclined at 35° to the horizontal, the Micro- 
scope can be easily supported by a side tube vertically above the 
crystal. The ordinary telescope serves for approximately centering 
and adjusting the crystal, while the more exact adjustment is made 
with the Microscope. According to the intensity of light from the faces 
of the crystal, the following methods of observation may be applied. 
(1) The complete Microscope is used. In the goniometrical mea- 
surements the faces belonging to one zone will then appear successively 
in the field of view. By arresting them at the maximum of their 
intensity “ Schimmer ” measurements are obtained. 
(2) By separating the whole Campani eye-piece, an image of the 
signal, as formed by the objective, is seen and can be used for approxi- 
mate measurements. 
(3) If the upper lens only of the Campani eye-piece be removed, a 
double appearance is seen on the reflecting face of the crystal. The 
face no longer shines wtth a uniform light, but gives a series of clear 
signals close to one another. The “ Signal-Schimmer ” measurements 
obtained by this means are more correct than those of (1). 
* Zeitschr. f. Wiss. Mikr., ix. (1892) pp. 128-30. 
