393 
are being held by the observer. These proportionally larger 
crystals of Tourmaline are gradually developed from a 
granular and indistinctly radiated mass which appears under 
the microscope as finely radiated or irregularly fibrous. The 
mineral in question fuses, under the blow-pipe, with but 
little effect at the edges and it gives distinct reactions of 
Boron, and very little of Fluorine.* 
Dr. Sommerlad has undoubtedly proved, from decimal 
analysis, that these light greyish blue masses of minerals are 
Tourmalines. 
Silicious Acid aie oat heres hap 36°86 
Aluminous Acid ... ce Sad at 36°72 
Boracic Acid “oe we 3M cus 10°56 
Peroxyde of Iron ... am i xt 5°66 
Peroxyde of Manganese ... i ee 0°66 
Lime Bit: ad oe u 88 Bee 0°34 
Magnesia a aes pe ade 3°92 
Kali (Potassium) ... ee eae a Ale lh 
Natrium ty: Ae, ig oh SOL 
Water ae cae Lae cuy AE TG 
Fluor AR ese cae ss Migs 0°61 
Total hee dale Spot (WES 
Specific Gravity ... 3°042. 
Criosinc REMARKS. 
According to the descriptions given by Messrs. Wintle and 
Geo. H. F. Ulrich of Mt. Bischoff, it would appear that, on 
the top of that mountain, there occurs a bold stockwerk-like 
mass of porphyry which has penetrated a non-fossiliferous, and 
very probably, very old formation of slate, sandstone and 
quartzite. These latter exhibit, in the immediate neighbour- 
hood, or, within the contact planes of the porphyries, great 
irregularities and considerable contortions in the bedding of 
the strata. 
Wintle speaks of tinlodes in this porphyry ; according to 
Ulrich, however, the tin ores occur as impregnations of the 
porphyry only, and principally so within the planes of 
contact with the schists. Ulrich reports also that the 
Waratah Company at the south-eastern flanks of the mountain 
is engaged in the exploitation of a lode (?) of Quartz-Porphyry 
carrying tin ore, which intersects independently the adjacent 
schistose (blue) formation. 
It is quite evident, from these descriptions, that the 
* These coarse needle-like aggregations of Tourmaline from Mt. 
Bischoff have that peculiar appearance, and remind strongly of those of 
Zeuxite. 
