470 Scientific Notices — Mineralogy. [Dec, 



Beryl, yellow, Quartz, daupliiny, 



Sulphate of barytes, Idocvase, 



Sulphate of stroiitites, Mellite 1 



Carbonate of lead, Native sulphur, 



Diopside, Garnet, 



Fluor spar, red and blue, Dichroite. 



" In examining the electricity of the tourmaline, I found that 

 it could be shown in a very satisfactory manner, by means of a 

 thin slice taken from any part of the prism. The experiment is 

 most advantageously performed, when the slice has its surfaces 

 perpendicular to the axis of the prism. When such a slice is 

 placed upon a plate of glass, and the glass heated to the temper- 

 ature of boiling water, the slice will adhere to the glass so firmly, 

 that even when the glass is above the tourmaline, the latter will 

 adhere to it for six or eight hours. In this way, slices of a very 

 considerable breadth and thickness are capable of supporting 

 their own weight. 



'O 



11 On the Existence of Pyro-electricity in Artificial Crystals. 



" It does not appear from any of Haiiy's writings, that he even 

 suspected the existence of pyro-electricity in crystals formed by 

 aqueous solution. In subjecting some of these to experiment, I 

 was surprised to find that they possessed this property, and 

 some of them to a considerable degree. The following is a list 

 of those in which I discovered it : 



Tartrate of potash and soda, 



Tartaric acid, 



Oxalate of ammonia, 



Oxymuriate of potash, 



Sulphate of magnesia and soda, 



Sulphate of ammonia, 



Sulphate of iron, 



Sulphate of magnesia, 



Prussiate of potash, 



Sugar, 



Acetate of lead, 



Carbonate of potash, 



Citric acid, 



Oxymuriate of mercury. 



" Among the preceding crystals, the tartrate of potash and 

 soda, and the tartaric acid, are pyro-electrical in a very consider- 

 able degree ; but the action of several of the other salts is com- 

 paratively feeble. 



" On the Pyro-electricity of the Powder of Tourmaline. 

 " Among the curious properties of artificial magnets, none is 



