1874.] Engineering. 123 
whilst the blue variety is essentially a mixture of white quartz and crocidolite. 
The fibrous character is, in both cases, due to the replacement of fibrous 
crocidolite by quartz; the brown variety being the product of a perfe& and 
slow alteration, whilst the blue is the result of an imperfect and rapid alteration. 
Among the ejections from the eruption of Vesuvius in 1872, there occurred 
certain minute crystals, which were described by Scacchi as a new species 
under the name of Microsommite. This species has recently received attentive 
study by Vom Rath, who, in spite of the unusually small size of the crystals, 
has had the patience and acuteness to examine them crystallographically. 
About 1500 of these little crystals, weighing together only ~,th of a gramme, 
have passed through his hands. The crystals are colourless hexagonal prisms, 
striated vertically, and terminated by dull basal planes. The hardness is 
about equal to that of felspar; and the specific gravity is 26. An analysis of 
the very small quantity at Vom Rath’s disposal yielded:—Silica, 33; 
alumina, 29; lime, 11'2; potash, 11°53 soda, 87; chlorine, 9°1; sulphuric 
acid, 1°7.. The following expression is given as the probable formula :— 
(2K,0,3CaO),A1,03,2Si02-+ NaCl+ 4,Ca0.SO3. 
The origin of microsommite may be traced to, the reaction of steam, charged 
with chloride of sodium, on the volcanic minerals leucite and augite. 
Under the name of Horbachite a new ore of nickel has been described by 
Dr. Knop, of Carlsruhe. In the neighbourhood of Horbach, near St. Blasien, 
in the Black Forest, there occurs a deposit of this ore, which has at different 
times invited exploration. The ore has been described as anickeliferous magnetic 
pyrites, but analyses of the pure mineral show that it is really a distin@ species. 
The mean of several analyses gives:—Sulphur, 45°87; iron, 41°96; nickel, 
1r‘98. From this result we may deduce the formula 4Fe2S3+Ni2S3. Knop 
calls attention to this association of sulphides as unique, no metallic sesqui- 
sulphides having previously been known to occur in a native state. 
Some recent observations by Dr. Schrauf, of Vienna, show that Brookite, 
one of the three native forms of oxide of titanium, must be referred to the 
oblique or monoclinic system. The crystals affect, however, a decidedly 
prismatic habit ; hence the reason why previous observers have placed this 
species in the prismatic system. Schrauf recognises three distinct types of 
crystal in brookite. 
Prof. Rammelsberg has laid before the German Geological Society some 
papers on mineral arsenides and sulphides. In one of these he discusses the 
mutual relations and the chemical constitution of the compounds of arsenic 
and antimony which occur native. He is led to regard the metallic arsenides 
not as true chemical compounds, like the sulphides, but as isomorphous 
mixtures of metal and arsenic; whilst the sulpharsenides are mixtures of 
these with bisulphides. What he says with respect to the compounds of 
arsenic applies also to those of antimony. 
Some beautiful crystals of Torbernite, or uranium-mica, have been recently 
raised in Cornwall, we believe from the neighbourhood of Redruth. They 
are notable for exhibiting an unusual development of the pyramid, so that 
the crystals are very different in general appearance from the common tabular 
forms. 
A preliminary description of the meteoric stone which fell, some years ago, 
at the Barratta Station, near Deniliquin, in Australia, has recently been 
published by Mr. Archibald Liversidge, of the University of Sydney. 
Nefediewite is a new Russian mineral, described by Pusirewsky. It seems 
to be an amorphous substance, resembling lithomarge. 
ENGINEERING—CIVIL AND MECHANICAL. 
Harbour Works.—On the 25th November last, Mr. L. F. Vernon Harcourt 
read a paper before the Institution of Civil Engineers on the construction and 
maintenance of Braye Bay Harbour, Alderney. This harbour was designed 
by the late Mr. James Walker, C.E., and the works in connection with its 
construction were commenced in 1847. The Admiralty intended, in the first 
