1896.] Mineralogy and Crystallography. 739 
with 3.01 per cent Mn,O,, and in another case with 1.91 per cent Cr,O, 
was prepared, but similar experiments with the oxides of nickel and 
cobalt were not successful, the rutile crystals containing no appreciable 
trace of NiorCo. Chromiferous crystals of cassiterite were also formed. 
It seems, therefore, that these substances have a peculiar affinity for 
the oxides of the type R,O,, but not for those of the form RO. 
Colored specimens of all three minerals become permanently lighter 
in color on heating. 
Marignac’s process for fusing zircon (i.e., with KF or with KF HF) 
was tried with rutile and cassiterite. Like zircon they both fuse rather 
readily, forming K, TiF, and K, SnF, respectively. 
Miscellaneous Notes.—Wiilfing® describes a simple apparatus 
for obtaining monochromatic light from direct sunlight. The experi- 
ments on quartz seem to show that the apparatus works with a good 
degree of accuracy. Measurements of the index of refraction of dia- 
mond gave for A,n==2.4024; for D, n=2.4175; and for H, n=2.4652. 
These are three of several values determined. The specific gravity of 
these diamonds referred to water at 4° was found to be 2.522.003. 
Hematite from Elba was also investigated, giving: 
w € 
2.904 2.690 for line A 
2.988 2.755 for line B 
3.042 2.797 for line C 
The specific gravity at 4° is 5.285+.002. A description is also given 
of a spectrum apparatus for use with a microscope or an axial angle 
instrument. In a later note’ Wiilfing gives a table comparing the 
values of the indices of refraction of the diamond obtained by himself 
with those determined by Walter; the agreement is very close. He 
states that either apparatus above mentioned may be obtained of Eug. 
Albrecht in Tiibingen. 
Kretschmer’ describes the occurrence of garnet, vesuvianite, wolla- 
stonite, epidote, augite, quartz and calcite at the contact of marble with 
granite near Friedeberg in Silesia. Minute details as to locality, asso- 
ciation and crystal form are recorded. 
Goguel® reports on. the crystal form, and in some cases on the opti- 
cal behavior of formopyrine, Cy, H,, N,O,, and its addition salts with 
5 Tscherm. Mitth., XV, pp. 47-76, 189%. 
6 Ibid, p. 350. 
1 Tscherm. Mitth., XV, pp. 9-28, 1895. 
8 Bull. Soc. Fr. Min., XVIII, pp. 27-31, 1895, 
