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4, Saxon GRANULITES— 
The granulite region of Mittweida in Saxony is surrounded 
and overlaid by gneiss and schists, and penetrated by numerous 
dykes and veins of granite, which Naumann considers to be of 
eruptive origin. Attention is now invited to the behaviour of 
a granulite, at the highest temperature, namely, at the fusion- 
point 1100°C, and for economical purposes of both varieties, 
granite and granulite. The recent establishment at Dresden, by 
Herr Frederic Siemens, of glass works and furnaces, is worthy 
of note: as it clearly shows that the granitoids can be turned 
to account in the arts. The glass from these works is now made 
from granulite, without the addition of any flux whatever. 
Some condensed particulars may be acceptable. At the first 
start, granite was melted and worked up into bottles or other 
ware, but it was soon found that the pyrite occurring in it was 
objectionable, and granite was therefore discarded for granulite, 
which is at present the only material used. The rounded grains 
of the quartz would lend themselves to the action of heat, and 
the orthoclase felspar and perhaps some albite in addition, 
which even under the common blow-pipe flame, will run into a 
white enamel. Felspathic glazes were used by the Chinese on 
porcelain ware ages ago, before they were introduced into 
Europe; prior to the year 1780, the glaze employed at Sévres 
contained no felspar; since that date, however, the use of an 
artificially prepared glaze has been abandoned, and recourse 
had almost exclusively to the granite, or haplite of St. Yrieix, 
near Limoges, a rock composed of felspar and quartz, and which 
has according to the analyses of M. Salvétat, the following 
chemical composition :— 
Silica Ae a a 74° 
Alumina ..- ae fe 18° 
Potash as 6 
Lime a am te 0: 
Magnesia ... 0 
Loss 0 
