186 Scientific Intelligence. 



which show distinct cleavage in the direction of the faces of the hexahe- 

 dron^ and are altogether so similar, that for a long time they were actually 

 mistaken for each other. Professor Mitscherlich now finds also that the 

 forms of the new seleniates are analogous to those of the sulphates ; and 

 what renders the discovery still more interesting is, that the salts may 

 be obtained in crystals superior in beauty even to the sulphates them- 

 selves. Among several very interesting species resulting from the new 

 acid, combined with the bases, was obtained an anhydrous seleniate of 

 ?oda, with a form corresponding to the anhydrous sulphate of soda, and 

 also to the sulphate of silver. It is very remarkable that the form of the 

 stileniate of magnesia is hemiprismatic, and the same as that obtained when 

 the sulphate of the same base is made to crystallize at a high temperature. 



8. Theory of the Formation of mineral waters. — Mr Struve of Dresden 

 has contrived to form saline solutions, very nearly agreeing with those found 

 in nature, by forcing pure water, or water impregnated with carbonic acid, 

 to pass under considerable pressure through pulverised portions of the rock 

 which occurs in the vicinity of the natural spring. The following instance 

 will give an idea of the extent of the resemblance in the solid contents of two 

 kinds of water, the one artificial, the other natural. The artificial solution 

 was formed by forcing first carbonic acid, and then water impregnated with 

 it, under a pressure of nearly two atmospheres, through a cylinder 84 inches 

 high, filled with 3 pounds 14 ounces of powdered clinkstone, and as much 

 of clean sand. The water began to.ooze out from the uppermost layer on- 

 ly about twelve hours after the beginning of the process. The natural 

 spring compared with it is the acidulous water of Bilin in Bohemia, a 

 country which in that vicinity abounds in clinkstone. 



Substances contained in 



16 ounces of water, 

 Carbonate of soda, 

 Muriate of soda, 

 Sulphate of potash, 

 Sulphate of soda. 

 Silica, _ - - 



Carbonate of lime, 

 Carbonate of magnesia, 



In the same manner Mr Struve has also produced saline waters similar 

 to those of Teplitz in Bohemia from the porphyry out of which the springs 

 there issue ; waters like some of Egra from the basalt of Liebenstein, near 

 Egra; and waters resembling the spring called the " Kreuzbrunn" at 

 Marienbad from the basalt occurring between Tepl and Marienbad. All 

 the appearances of natural mineral springs may be explained by a theory 

 corresponding to the facts observed.-— (Schweigger's Journal, vol. xvii. 

 p. S74.) 



9. Caustic Potash. — We have received the fdllowing notice from Mr T. 

 Graham. '' In dissolving the caustic potash in sticks of the apothecaries. 



