140 On the Mineral Waters of Carlsbad. [Aug. 



an uneven fracture, and bear a close resemblance to magnesite 

 [dolomite?] or gurhofite. 



Before the blowpipe, the sprudelstone swells somewhat, loses 

 its colour, and either falls to powder of itself, or may be reduced 

 to that state by the slightest pressure. If the experiment be 

 made in a small glass matrass, some water is rendered visible ; 

 and the quantity of water disengaged is proportional to the 

 radiated structure of the stone. Now this is a distinctive 

 character of arragonite ;* between which and the sprudelstone 

 there is a remarkable similarity in their fibrous texture, in their 

 total want of any foliated structure, in their specific gravity, in 

 the alterations which they undergo when ignited, and in their 

 containing a certain quantity of water, and of carbonate of 

 strontian. The compact sprudelstones contain little or no 

 water ; and acquire no tendency to disintegration by being 

 calcined. 



1. The following I ascertained to be the composition of two 

 sprudelstones, which approached pretty closely to one another 

 in the nature and relative proportion of their constituents. The 

 first is the incrustation which is deposited upon the exterior sur- 

 face of the tin vessels mentioned in p. 129. The second is a 

 brown, fibrous, and very compact variety, which is frequently 

 cut into ornaments. Specific gravity 2"863. 



Water 1-59 1-40 



Carbonate of lime 96-47 97-00 



Carbonate of strontian. 0-30 0*32 



Fluateoflime 0-99 0-69 



Phosphate of lime .... 0-06 ~\ 



Phosphate of alumina. . 0-10 > 0*59 



Oxide of iron 0-43 J 



Oxide of tin 0-06 



Oxide of manganese . . Trace 



100-00 100-00 



2. A white variety, partly granular and partly delicate fibrous 

 in fracture, on being dissolved in muriatic acid, left a semitrans- 

 parent substance, which was converted into a white powder by 

 desiccation. This substance was fluosilicate of potash ; for it 

 was fusible before the blowpipe, sulphuric acid disengaged from 

 it fiuosilic acid, and the residue consisted of sulphate of potash. 

 Ammonia threw down from the solution a yellow-coloured pre- 



* That this property is not possessed by every variety of fibrous limestone may be easily 

 proved by heating fragments of sattin spar, arragonite, and sprudelstone, in a small 

 glass matrass before the blowpipe. The arragonite, and soon after the sprudelstone, 

 fall to powder ; but the sattin spar continues wholly unaltered. The richer the arrago- 

 nite is in strontian, the speedier is its disintegration. 



