418 Chronicles of Science. [July, 
dritic forms which, under the microscope, were found to consist of 
radiating fibres having a cellular structure. These were evidently 
low vegetable organisms developed from spores which were deposited _ 
from the atmosphere, since similar specimens dried in vacuo were 
destitute of such appearances. It is possible, then, that vegetable 
life may be developed in siliceous solutions during solidification. 
Mr. David Forbes has published the second part of his “ Re- 
searches in British Mineralogy.” * In this paper he describes the 
occurrence of a sulphide of iron and nickel—probably a nickel- 
liferous pyrrhotine—near Inverary Castle, in Argyleshire, and also 
at the Craigmuir nickel-mine, near Inverary. Our author calls 
attention to the tendency of nickel to associate itself with pyrrho- 
tine or magnetic pyrites; whilst the allied metal, cobalt, prefers 
association with the ordinary iron pyrites. The same paper contains 
a notice of an arsenio-sulphide of nickel, referred to the species 
Gersdorfite, also found in the Craigmuir nickel-mine. An abstract 
of both the first and second parts of Mr. Forbes’s “Researches” will 
be found in the ‘Geological Magazine.’} 
The exceedingly rare arseniate of copper called Cornwallite has 
been lately examined by Professor Church, who shows that the 
mineral contains only two equivalents of combined water, instead of 
five, as hitherto supposed. Its amended formula is thus given,{ 
using of course the new equivalents :— 
Cu, 2 As O,, 2 Cu H, O,, aq. 
At length mineralogists are beginning to recognize the value of 
the microscope as an aid in their investigations. Herr Zirkel, whose 
name must be familiar to every geologist in connection with his 
admirable ‘ Petrographie,’ has recently laid before the German Geo- 
logical Society his researches “On the Microscopic Structure of 
Leucite, and the Composition of Leucite-bearing Rocks.”§ Many 
erystals of this mineral exhibit, on section, a number of included 
glass-like particles and acicular bodies, either accumulated in the 
centre or symmetrically distributed around the margin of the crystal. 
The use of polarized light reveals a beautiful system of alternate 
dark and light lines, bearing a relation to the micro-lamellar struc- 
ture of the mineral. 
In a paper on the Basaltic Rocks of the Lower Main Valley, 
Herr Hornstein describes a new mineral to be called Nigrescite. | 
It occurs in the anamesite of Stemmheim near Hanau, and may pos- 
* ‘Philosophical Magazine,’ No. 236, p. 171. 
+ May, 1868, p. 222. 
t ‘Chemical News,’ April 10, p. 175. 
§ ‘ Zeitschrift d. Deutsch. Geolog. Gesell.’ Bd. xx., Hft. 1, p. 97. 
\| ‘Zeitsch. d. Deutsch. Geol. Gesell.’ Bd. xix., p. 342; ‘Neues Jahrb. f. Mine- 
yalogie, 1868, Heft 2, p. 202. 
