1872.] Mineralogy. 389 
Henderson’s treatment, have been tested by Mr. Kirkaldy, and found to stand 
a very high tensile strain. 
At a recent meeting of the Institution of Civil Engineers, Mr. I. Lowthian 
Bell read an interesting paper on the conditions which favour and those which 
limit the economy of fuel in the blast-furnace. As iron-smelting consumes 
nearly one-sixth of all the coal raised in the country, it is important that the 
highest degree of economy should be practised. Having determined the 
quantity of heat absorbed in the process of smelting, and the calorific power of 
the fuel employed, Mr. Bell proceeds to deteymine the weight of combustible 
necessary to produce the required effet. Assuming that the ore yields 40 per 
cent of pig-iron, and requires 15 cwts. of limestone as flux, it will need 
theoretically about 25} cwts. of ordinary Durham coke to produce a ton of 
iron. Mr. Bell discusses the theory of the hot-blast, and believes that its 
values lies in this principle—that the rate of reduction must not proceed less 
rapidly than that of fusion. By constructing the furnace sufficiently large the 
use of hot-blast may be dispensed with, and yet no fuel sacrificed. Beyond a 
certain limit, however, no advantage is gained by increasing the capacity of 
the furnace. 
Mr. E. F. Mondy has called attention to the magnetic properties of certain 
copper-slags. Several specimens of ore-furnace slag exhibited strong polarity ; 
those which presented a porphyritic appearance from included fragments of 
quartz, being more strongly magnetic than a vitreous specimen. Polarity was 
also evident, though to a less extent, in crystallised metal-slag and in roaster- 
slag. Feeble magnetism was also exhibited in refinery-slags. 
In the April number of the “‘ Journal of the Royal Institution of Cornwall,” 
Mr. J. H. Collins publishes a note on a portion ofthe incrusted surface of a block 
of jew’s tin found on Tremathack Moor, in the parish of Madron, and recently 
acquired by the Institution. All ancient blocks of tin pass in the West of 
England under the name of ‘“ Jew’s tin,” whatever may have been their origin. 
The block in question was partially coated with a hard, brittle, brown incrus- 
tation, which was found to contain go’62 per cent of binoxide of tin, 1°66 of 
chloride of tin, 1°04 of peroxide of iron, 0°43 of metallic tin, 0°41 of silica, and 
the rest of moisture evolved at 120° C. 
MINERALOGY. 
For a long time mineralogists were acquainted with only a single species of 
crystallised silica. This was the well-known and ubiquitous mineral— 
common Quartz—a mineral which, as every one knows, crystallises in the 
hexagonal system, and has a sp. gr, of 2°6. Not long ago Professor Vom 
Rath showed that silica was dimorphous, and described under the name of 
Tridymite a new species which had a sp. gr. of only 2°3, and yet crystallised 
in the hexagonal system, but with different parameters from those of quartz. 
We now learn that silica is trimorphous, for a third form of crystallised silica 
has been discovered by Professor Nevil Story-Maskelyne, F.R.S. For this 
new species the name of Asmanite is proposed—a name fancifully derived from 
Asman, the Sanscrit term for the thunderbolt of Indra. Indeed, Asmanite is 
a meteoric mineral, and was detected among the constituents of the meteorite 
which was found in 1861 at Breitenbach, in Bohemia, and is now deposited in 
the British Museum. Asmanite has a low sp. gr. (2°245), and in this point 
resembles Tridymite, from which it totally differs, however, in crystalline 
form. Optical examination shows that it is a biaxial mineral, and crystallo- 
graphic measurements prove that it belongs to the orthorhombic or prismatic 
system. It is difficult, however, to measure the specimens, for the mineral 
occurs only in minute grains, more or less rounded, and exhibiting but few 
crystalline faces. Professor Maskelyne has nevertheless determined the ratios 
of the parameters of the crystals, and the inclination of the optic axes. Its 
hardness is 5°5._ Two analyses show that it consists essentially of silica, and 
contains but a small percentage of foreign matter. The Asmanite is asso- 
ciated in the Breitenbach meteorite with enstatite, chromite, troilite or 
meteoric pyrites, and nickeliferous iron. 
