1825.] M. Berzelius's Hypothesis of the Atomic Theory. 355 



rately by chemical processes, and compounds of different bases 

 combined with the same acid." M. Mitscherlich has quoted 

 three crystallized substances found in nature as analogous to 

 those he obtained artificially, namely, the sulphates of lead, 

 baryta and strontita. " These analogous compounds," observes 

 M. Haiiy, " of three bases combined with the same acid should 

 have the same primitive form, and M. Mitscherlich without 

 doubt has examined closely into the matter to satisfy himself if 

 this example be favourable to his views. The fact is obviously 

 otherwise. The primitive form of sulphate of lead is a rectan- 

 gular octohedron, and consequently incompatible with that of 

 sulphate of baryta and sulphate of strontita, which is a right 

 rhomboidal prism. Moreover the angles and dimensions of this 

 prism differ obviously in the tv.'o species, the angles of the base 

 in the sulphate of baryta being 101° 32' and 78° 28', and in sul- 

 phate of strontita 104° 28' and 75° 12'. 



" M. Mitscherlich has not been more fortunate in the identity 

 of form which he fancies he has discovered between two other 

 natural substances, whose composition has nothing in common, 

 namely, sulphate of copper and axinite. The three angles which 

 measure the incidences of the faces oftheparallelopipedons, the 

 primitive form of those two substances, are, for the sulphate of 

 copper, the first 124° 2'; the second 128° 37'; and the third 

 109° 32'; whilst for axinite two are right angles, and the third 

 is 101° 30'. Such are the contrasts which M. Mitscherlich 

 takes for characters of identity." 



The form of the crystals of sulphate of magnesia and sulphate 

 of zinc is, according to Haliy, a right prism with a square base, 

 terminated very commonly by a right quadrangular pyramid. 

 M. Mitscherhch quotes them as " another example, but the 

 angle," says Haiiy, " formed by two of the faces of the pyramid 

 taken on two opposite sides is about 10° greater in the sulphate 

 of magnesia than in the sulphate of zinc. 



" Moreover, how is it that the results announced by M. Mit- 

 scherlich are, on every side, in contradiction to those presented 

 by natural productions, as if affinity played a different part in his 

 laboratory to that which it acts in the laboratory of nature ? 



" Take a view of the various crystals that are found in our 

 cabinets containing different bases united to the same acid, and 

 throughout their geometrical forms will be seen to differ more or 

 less. The primitive form of phosphate of lime is a regular hex- 

 ahedral prism, that of phosphate of lead a rhomboid, that of 

 phosphate of iron an oblique rectangular prism, that of phosphate 

 of copper a rectangular octohedron, and that of phosphate of 

 manganese a rectangular parallelopipedon. If we take the 

 muriates, the primitive form of muriate of ammonia is a regular 

 octohedron, that of silver a rectangular parallelopipedon, that of 



2 A 2 



