Dr. Du Riche Pretter — Mineral Springs of Baden. 151 



white Jura (Malm) and of Middle or brown Jura (Dogger), the 

 intermediate strata of Lias, and the central or lowest strata of 

 Keuper (Trias), which last-named therefore lies in the axis of the 

 anticlinal fold. The more or less uniform character of this section 

 throughout the ridge is attested by the fact that the various mineral 

 springs rise from along the line of junction of the Keuper and the 

 younger strata. 



The distinctive features of the four varieties of mineral springs 

 in the district, and of their occurrence, may be briefly stated as 

 follows: — 



1. Baden Springs, 360 metres (1180 ft.) above sea-level. 1 As is 

 seen from the plan, Fig. 4, all the Baden springs rise in a sharp 



N 



Fig. 4. — Mineral springs of Baden, Switzerland. 



curve of 60 degrees formed by the Limmat at a point where the 

 river has eroded the glacial gravels of the valley to a depth of about 

 20 metres, or 66 ft., down to the Keuper, which at this point crosses 

 the bed of the river. The springs issue through fissures between the 

 Keuper and the Jurassic strata which, as already shown in the trans- 

 verse section, cross the valley in two separate ridges, forming the 

 Baden basin. On the left bank of the river, the Keuper is overlain 

 by about 30 ft. of clay and marl, which, somewhat further down the 

 river, are overlain by sand and glacial Nagelfluh to a depth of about 

 66 ft. On the right bank, the same clay and marl, alternating with 

 gypsum bands, are about 50 ft. in depth, and overlie a compact 

 dolomite. 



The springs on both sides of the river number twenty-one, while 

 about fifteen more issue in the river-bed and are lost. The principal 

 mineral constituents of the water are, in 1,000 parts : sulphate of 

 sodium, 1*84:2 ; chloride of calcium, 1*3 ; chloride of sodium, 0-3 ; 

 bicarbonate of magnesium, 0'3 ; and some free sulphuretted hydrogen. 

 As is seen, these constituents are the products of the decomposition 

 and reaction upon each other of the principal compounds composing 

 the rocks characteristic of the Middle Keuper formation — to wit, 

 gypsum (sulphate of calcium), common salt (chloride of sodium), 

 and dolomite (carbonate of magnesium). 



1 These springs have been known for nearly 2,000 years, Baden having been, like 

 Windisch (Vindonissa), near Turgi, four miles below Baden, occupied by the Romans 

 as early as 61 b.c. 



