440 M. Stromeyer on Polyhalite. [Dec. 



Sulphate of lime combined with water . . 28-2548 



Anhydrous sulphate of hme 22'42] 6 



Anhydrous sulphate of magnesia 20*0347 



Sulphate of potash 27-7037 



Muriate of soda 1910 



Red oxide of iron 0-3376 



98-9434 



From a comparison of the quantities of these sulphates 

 contained in polyhalite, it is plain that they enter into the conr- 

 position of this fossil in the proportion of their equivalent 

 numbers. 



This point is of considerable importance, since it clearly proves 

 that they are not by any means mechanically or fortuitously 

 mixed with each other, but chemically united so as to form a 

 real combination. By which is proved beyond a doubt that 

 polyhalite constitutes a peculiar mineral substance differing from 

 all the other minerals of this class. 



It is nevertheless uncertain what place in the mineral system 

 should be assigned to polyhalite, especially as we are by no 

 means acquainted with its real structure and conformation ; and, 

 therefore, cannot at present decide and determine upon which 

 of its constituent salts, its physical constitution principally 

 depends. 



But as this fossil differs from the rest very much on account 

 of the sulphate of potash which it contains, it appears to me 

 that it would be better and most consistent to exhibit it in the 

 interim as a peculiar species of the salts of potash. 



Article VIII. 



On the Theory of Franklin, according to u-hich Electrical Pheno- 

 mena are explained bi/ a single Fluid. (A Memoir read at the 

 Royal Institution of the Sctences at Amsterdam.) By Martin 

 VanMarum, Knight of the Order of the BelgicLion, Secretary 

 of the Dutch Scientific Society, Director of the Teylerian Mu- 

 seum, &c. &c. 1819. (With a Plate). Translated from the 

 French. 



Is there any solid objection against the theory of Franklin 

 which attributes electrical phenomena to a single Jiuid, or are they 

 to be referred to two different fuids of an opposite nature ? 



When I caused the large electrical machine to be constructed 

 for the Teylerian Museum in 1784 for the purpose of observing 

 some phenomena on a larger scale by means of the electrical 

 non-equilibrium, and thereby to procure the means necessary to 



