Ixxxvii 
into several simple forms by different solutions and successive 
slow crystallizations. Thus cubo-octo-dodecahedral alum yield- 
ed separate octahedrons, cubes, and cubo-dodecahedrons. 
16. Crystals of a certain form being put into a solution of 
the same substance, which gives naturally a different form, in- 
crease by additions according to this new form.—(See Ann. de 
Chim. et Phys. viii. 5.) 
Vv. ELECTRICITY OF MINERALS. 
° Mineralogy. 
M. Haiiy, assisted by M. Delafosse, has made a very elaborate 
set of experiments to determine the electrical state of the dif- 
ferent species of minerals. I can here give nothing more than 
a tabular view of the results which they obtained. This, indeed, 
is sufficient, as the mode of trying the electricity of minerals 
has been long familiar to mineralogists. 
CLASS I. 
Substances transparent and colourless in their perfect state. 
Their colour, when they have any, depends upon an accidental 
principle. They are capable of insulating, and acquire, when 
rubbed, the vitreous or positive electricity. 
ORDER I. 
Electrical by Heat. 
Borate of magnesia, 
Silico-fluate of alumina, 
Axinite, 
Tourmaline, 
Mesotype, 
Prehnite, 
Oxide of zinc, 
Titane siliceo-calcaire. 
ORDER Il. 
Nonelectric by Heat: 
A. Saline. 
Calcareous spar, 
Ditto, containing magnesia in 
lamine, from St. Gothard, 
Arragonite, 
Phosphate of lime (asparagus 
stone), 
Fluate of lime, 
Sulphate of lime, 
Ank drous ditto, 
Sulphate of barytes, 
Carbonate of barytes, 
Sulphate of strontian, 
Carbonate of strontian,: 
Sulphate of magnesia, 
Silico-borate of lime, 
Nitrate of potash, 
Sulphate of potash, 
Common salt, 
Glauberite. 
B. Earthy. 
Quartz, 
Zircon, 
Corundum 
Cymophane, 
Spinel, 
Beier. 
Euclase, 
Dichroite, 
