390 Progress in Science. [July, 
Professor Viktor Von Lang has published an account of the crystalline form 
of Guarinite, a mineral resembling sphene. This mineral was described by 
Guiscardi, who referred it to the tetragonal or pyramidal system; but the 
author shows that, from the optical characters of specimens in the British 
Museum, it must be transferred to the rhombic system, although the angles of 
the crystals and their general habit closely resemble those of a tetragonal 
mineral. The same distinguished physicist publishes his crystallographic 
determinations of the form of the rare mineral Leucophane. 
In examining some of the fing crystals of cuprite, or red oxide of copper, 
from near Liskeard, Professor Schrauf, of Vienna, has detected an icositetra- 
hedron of the value 322, and therefore new to this species. 
A note on the occurrence of cobalt in connection with the tin ores of Corn- 
wall has been published by Mr. R. Pearce in the ‘‘ Journal of the Royal Insti- 
tution of Cornwall.”” The author has found cobalt in a sample of tin-stone 
from Dolcoath Mine, where it probably occurs as an arsenide of cobalt in the 
mispickel, or white arsenical mundic, associated with the tin. He also finds 
that the furnace-produc& known to tin-smelters as ‘‘ Hard-Head,” contains 
cobalt derived from the tin ore which may have come from different localities. 
One specimen of hard-head contained 4°4 per cent of cobalt, and Mr. Pearce 
suggests that its extraction may be profitable, especially if the tin can at the 
same time be obtained, as the specimen in question yielded as much as 16°25 
per cent of tin. 
Two new instances of pseudomorphism are recorded in ‘‘ Poggendorff’s 
Annalen,” by M. Helland, of Christiania.” One of these is a pseudomorph of 
mica after garnet from Rést6l, near Arendal, in Norway. The garnet is an 
iron-alumina variety, rich in manganese, and occurs in small icositetrahedral 
crystals of a reddish brown colour in a veinstone of pegmatite composed of 
orthoclase, oligoclase, and mica. Some of the crystals, while retaining their 
form, have become converted into a green potash-mica. A nucleus of un- 
changed garnet remains in the centre of some of the partially altered crystals. 
The second pseudomorph consists of steatite in the form of augite, and occurs 
at Snarum, not far from the locality which yields the celebrated pseudomorphs 
of serpentine after olivine. 
It has been recently found by Professor Zirkel that the felspathic mineral 
called Bytownite, usually grouped with the lime-soda felspars, so far from 
being a pure and homogeneous mineral, is made up of at least four distiné 
constituents. Microscopic sections show that it is really a crypto-crystalline 
rock containing a triclinic felspar, a green hornblende, a mineral taken to be 
quartz, and black granules of magnetic iron. Henceforth, then, Bytownite 
must be expunged from our text- books on mineralogy. 
Some experiments on the alteration which felspars suffer by the action of 
saline solutions and other agents have been made by M. H. Birker and 
R. Ulbricht, and are of interest as bearing upon the natural weathering and 
alteration of felspathic minerals. The felspar used contained 8°51 per cent of 
potash, 3°37 soda, 1°3 baryta, 16°03 alumina, and 65°52 of silica. The action 
of the several agents was allowed to go on for 24 years. Distilled water had 
practically the same solvent action, whether it contained air ornot. Carbonate 
of lime, nitrate of lime, and several other salts exerted but little more action 
than water alone. Carbonic acid, and carbonate of lime with carbonic acid, 
increased the action on the alkalies and the silica. Lime-water dissolved more 
of the felspar by acting on the silica; sulphate of ammonia had an energetic 
action ; but of all the agents used magnesia was found to be the most active. 
Aset of useful Mineralogical Tables, arranged by Dr. J. Emerson Reynolds, has 
been published in a recent number of the ‘‘ Journal of the Royal Dublin Society.” 
Although compiled primarily with a view to facilitate the examination of the 
fine mineral collection in the possession of the society, these tables admit of 
much wider use, inasmuch as they contain a considerable amount of general in- 
formation, and form indeed a concise synopsis of the mineral kingdom. The 
crystalline system, chemical formula, lustre, colour, hardness, and specific 
