332 Notices and Extracts from the Minutes of the Geological Society. 



is not found in ridges {en sillons), nor in beds alternating with the gypsum, 

 but that it is of contemporaneous formation with that rock. It is found in 

 crystaUine laminae of several lines of thickness (and not in grains nor in regu- 

 lar crystals), filling up the fissures of the gypsum, and also the interior of that 

 rock without regularity. It appears, nevertheless, that the sulphate of soda is 

 disseminated in a direction parallel to the stratification of the gypsum; for the 

 fracture of the rock in that direction exposes more of the salt than a tmns- 

 verse fracture. 



The co-existence of sulphate of lime and sulphate of soda in the same rock, 

 is as remarkable as the binary union of sulphuric acid with those bases in the 

 glauberite, which is composed of those two sulphates in nearly equal propor- 

 tions and in intimate union. In the gypsum of Muhligen, on the contrary, 

 this double combination takes place separately, the two sulphates being asso- 

 ciated, but without chemical mixture, — since there is not an atom of lime in 

 the sulphate of soda, nor an atom of that alkah in the sulphate of lime. They 

 are so separated, although forming an integrant part of the same rock, that it 

 is easy to detach crystals of sulphate of soda from the gypsum, to which their 

 adherence is very feeble ; — a surprising circumstance, if we consider them to 

 have been dissolved together and to have received solidity at the same time. 

 It is difficult to conceive how the integrant molecules of the sulphates of lime 

 and soda have not been intimately united in this rock, as in the glauberite, — 

 a difference which perhaps depends upon the proportions. 



This sulphate of soda is not, however, without mixture ; for it contains a little 

 iron and hydrochlorate of soda, which is attested by the bluish tint produced 

 by the hydrocyanite of potash, and the flocculent heavy precipitate formed by 

 the nitrate of silver. 



Mr. Prey of Aarau, a skilful chemist to whom I sent a pound of the salt, 

 analysed it by order of the cantonal society of Argovie. He has not merely 

 proved the presence of the two salts, but he has determined their proportions 

 per cent as follows : — 



Sulphate of soda (dry) 44*4425 



Hydrochlorate of soda 55"4571 



Water of crystallization .... 0-1004 



100-0000 

 Iron, — an indeterminable trace. 



The quantity of this salt contained in the gypsum cannot be determined, be- 

 cause it is strewed over the beds very unequally. The experiments which 

 I have made have given me different proportions, from 4^ to 10 per cent. 

 The property which sulphate of soda possesses, of losing its water of crystal- 



