§ 5. THE CHELTENHAM WATERS. 543 



other properties, and become what are termed mineral 

 waters ; such is the origin of the celebrated Cheltenham 

 waters.* 



The town of Cheltenham is built on Lias clays and 

 marls, beneath which, but at a great depth, lie the Trias - 

 sic deposits, the reservoir of the rock-salt and brine - 

 springs, whence the mineral waters have their origin, 

 and derive their saline ingredients ; but these undergo 

 various modifications in their passage to the surface through 

 the superincumbent beds of Lias, which are full of iron 

 pyrites, and sulphate of lime. From the analyses of these 



Cheltenham. 



Ltgn. 121.— Section of the Lias at Cheltenham. 



(From Sir R. I. Murchisori's Sil. Syst.) 



1, 1. Red marl. 2, 2, 2. Origin of the Cheltenham waters. 3, 3. Lias clays 

 and marls. 4. Alluvium. 



waters, it appears " that their principal constituents are 

 the chloride of sodium (muriate of soda) or sea-salt, and 

 the sulphates of soda and magnesia. Sulphate of lime, 

 oxide of iron, and chloride of magnesium, are present in 

 some wells only, and in much smaller quantities. Besides 

 these ingredients, iodine and bromine have been detected 

 by Dr. Daubeny, who instituted experiments to ascertain 

 whether these two active principles, which the French 

 chemists had recently discovered in modern marine pro- 



* See Sir R. I. Murchison, on the mineral springs of Gloucester- 

 shire and Worcestershire. Silurian System, p. 34. 





