Notices and Extracts from the Minutes of the Geological Society. 331 



3. — Translation of a Letter from Mons, de Gimbernat^ of Geneva, to G. B, 

 Greenough, Esq. V.P.G.S. ^c. [Read April 7th, 1826.] 



The sulphate of soda which I have the honour to send to you, and which I 

 request you to present to the Geological Society of London, was discovered in 

 the gypsum which is worked by means of two galleries at a quarter of a league 

 from Muhligen, on the left bank of the Reuss in the Canton of Argovie. I 

 found this crystallized amorphous salt most abundantly in the northern gal- 

 lery. Having observed saline efflorescences in a mass of gypsum near a mill 

 where that substance is reduced to powder, I had the curiosity to examine the 

 quarry from whence it was extracted, and I there saw by lamp light, that the 

 recent fractures were studded with sparkling layers, as in mines of rock salt. 

 I perceived by the taste that these crystals were sulphate of soda, and that the 

 while powder spread over the walls of the gallery was the same salt which had 

 effloresced, losing its water of crystallization by contact with the atmosphere. 

 The length of the gallery is about 320 feet, breadth 6, and average height 

 about 13 feet. From its entrance on the banks of the Reuss to the present works, 

 several beds of compact gypsum were traversed; these beds were granular, 

 shelly, of a grayish white colour, and void of salt. In the beginning of this 

 year some saline beds were cut through, which were below those above men- 

 tioned : but the country people, who work this gypsum on their own account, 

 paid no attention to the discovery ; so that the existence of native sulphate of 

 soda in Argovie was unknown at Aarau in May 1825; when I sent specimens 

 of it to the Society of Natural Sciences of the Canton, with a notice upon the 

 position of the salt, and containing hints as to the mode of working it advan- 

 tageously. However, as a manufacture of sulphate of soda by the decomposition 

 of sea-salt had just been established at Aarau, little importance was attached 

 to this discovery, nor to the instructions for quarrying the salt, the advan- 

 tages of which will be probably lost, owing to the bad management of the 

 present works, which are conducted on principles contrary to all the rules of 

 mining. 



There are three beds of secondary gypsum interspersed with crystallized 

 sulphate of soda, and separated by a thin deposit of foliaceous marl containing 

 the same salt, but in less quantity than the gypsum. The 1st or upper bed 

 is three feet thick, the 2nd five feet, and the 3rd (which is little cut into) 

 presents a section of two feet. Thus this saliferous formation is at least ten 

 feet thick; the depth is unknown, the beds being nearly vertical. 



In stating that the salt is there disseminated, it must be understood tiiat it 



