62 
THE PRINCIPAL FLOOR. 
by the spathose ores of the Exmoor hills in Devonshire, the' 
Brendon hills in Somersetshire, and Weardale in Durham. 
Spiegeleisen is also obtained in some of the Continental works 
from manganesiferous hematites, and it is likewise smelted from 
the residues obtained in the treatment of mixed ores of iron and 
zinc at Newark in New Jersey. The latter process is well 
illustrated in the Case before us. After the greater part of the- 
zinc has been removed from the ore, the cinder-like residue is 
smelted for spiegeleisen. This residue contains all the iron and 
manganese originally present in the franklinite, one of the chief 
minerals in the mixed ore. The bright green colour of the slag 
accompanying the spiegeleisen is due to the presence of 
manganese. The proportion of manganese in the spiegeleisen 
varies considerably in different specimens ; one example 
exhibited, from Laibach in Carniola, contains as much as 14 per 
cent. If the proportion exceeds 20 per cent, the alloy is known 
as ferro-manganese, which is used for the same purposes as 
spiegeleisen. In ferro-manganese the proportion may rise to 
nearly 90 per cent. 
On the opposite side of this Case will be found a series of 
specimens illustrating the smelting of the brown iron ores of the? 
Coral Rag — one of the sub-divisions 'of the series of middle 
oolites — as carried on at Westbury in Wilts. 
A portion of this Case is temporarily occupied by specimens 
showing the powerful agglutinating action of oxide of iron. 
Slags and Crystalline Furnace Products. Case JS To. 12. 
Among the more notable specimens of crystalline products in 
this Case, attention may be directed to some fine examples of the 
bright copper- red cubic crystals of a peculiar compound of 
titanium (p. 71), not unfrequently found in the “ bear ” of blast 
furnaces. These crystals were formerly thought to be pure 
titanium, but are now known to consist of nitride of titanium 
with cyanide of titanium. The specimens of crystallised oxide 
of zinc from the iron furnaces of Westbury are also interesting. 
The fine specimen of a furnace-product having the composition 
of magnetic oxide of iron and exhibiting an aggregate of 
octahedral crystals, will not fail to catch the visitor’s eye ; nor 
will the other artificial minerals escape attention, such as the 
crystals of galena from the Freiberg lead furnaces, or of 
orthoclase from the Hartz copper- works. There is also 
exhibited here a beautifully crystalline compound of peroxide of 
iron and lime, thus related in composition to the natural group 
of spinels, which was prepared by the late Dr. Percy. 
The opposite half of this Case contains some interesting forms 
of slag , several of which are crystallised ; in some cases these 
resemble, both in form and in composition, certain minerals. 
The utilisation of iron-slags from blast-furnaces is illustrated 
by specimens showing their use for making concrete and 
cement, for ornamental castings and for the production of 
