Dr . Brewstep, on the laws of polarisation , &c. 225 
It appears from the slightest examination of the preceding 
Table, that all the crystals with one , two, or three axes, range 
themselves under their particular primitive forms, and that 
the only exceptions to this general fact, are Idocrase and Apo- 
phyllite, which we have no doubt will be found to have pri- 
mitive forms, different from those assigned to them by Hauy. 
All the crystals with one axis have for their primitive forms 
a hexaedral prism, a rhomboid with an obtuse summit, and 
an octohedron in which the pyramids have a square base. 
All the crystals with three axes, have the cube, the regular 
octohedron, and the rhomboidal dodecahedron for their pri- 
mitive forms ; and all the crystals with two axes, crystallize 
in the various other forms given in the Table. 
Hence we are furnished with the means of deducing the 
number of axes in crystals from their primitive form, and 
of approximating to the primitive form when the number 
of axes is given, by excluding certain other primitive forms 
which belong to a different number of axes. If Hauy and 
Bournon have given these forms correctly for the following 
substances, in which I have not detected the number of 
the axes, they will be arranged as in the annexed Table. 
One Axis. 
Tungstate of lime. 
Octohedrite. 
Ruby silver. 
Cinnabar. 
5 Carbonate of strontian. 
Dioptase. 
Harmotome. 
Chabasie. 
Cryolite. 
10 Phosphate of lead 
Glacial sulphuric acid. 
Carbonate of barytes. 
Pinite. 
Spioellane. 
MDCCCXVIII. 
r~ — — ~ — — 
Euclase. 1 
Calamine. 
Corundum. 
Staurotide. 
5 Datolite. 
Sphene. 
Titanite. 
Wernerite. 
Meionite. 
10 Paranthine. 
Acetate of barytes. 
Calomel. 
Arseniate of potash. 
Green Carbonate of coi 
Gg 
> Axes. 
> 
Arseniate of copper in ob- 
tuse octohedrons. 
Molybdate of lead. 
Realgar 
