﻿MM. SCHLAGINTWEIT ON THE ALPS. 



27 



of limestone of considerable interest. Masses of gneiss, hornblende 

 rock, and mica-schist, of different widths, form some not always very 

 distinct radiating groups, similar to such as are so frequently seen in 

 the crystalline slates of the Western Alps. Detailed accounts of 

 these rocks succeed ; after which we have the geology of the Tauern 

 Alps in the Upper Moll district, preceded by a list of the geological 

 authors who have treated of this Alpine "group" (p. 228). 



The Tauern are a lofty chain of crystalline rocks, forming a part 

 of the Rhsetian Alps. Especially in the north of this range the Alps 

 exhibit a great regularity, for here there succeeds a district of tole- 

 rably developed Transition rocks, whereon the vast range of the 

 northern limestone Alps in Salzburg and Bavaria are elevated. 



The composition of this extensive "group" is somewhat various. 

 Gneiss and mica-schists predominate ; between these rocks occur 

 great masses of chlorite slates, of hornblende rock, of calcareous 

 schists, and of calcareous mica-schists. Granite also and isolated 

 patches of serpentine are found at many points. The geological cha- 

 racters of this district follow in considerable detail. 



M. Adolph Schlagintweit, in Chapter xi.* (pp. 235-273), dwells 

 upon the Formation of Springs and their different Temperatures, and 

 on the Geothermal conditions of different Alpine districts. He finds 

 that; — 1. In using the springs for the determination of the local 

 temperatures of the earth, it is indispensable that, in arriving at 

 comparable results, we direct our attention to the geological forma- 

 tions and local conditions, on which the nature of the origin of springs 

 is necessarily dependent ; — 2. The origin of springs is not only con- 

 nected with the mode of stratification, but also, and that most inti- 

 mately, with the general character of the rock formation ; — 3. The 

 fissures and porosity of limestone give rise to important differences 

 in the conditions attendant on this rock and on crystalline schists. 

 In limestone the springs are rare, copious, and, coming through this 

 rock from other higher districts, often issue with a much lower tem- 

 perature than usually found in springs flowing out at such a level ; — 

 4. The altitude at which the last springs can occur depends on the 

 general elevation of the mountain-mass ; their distance from the mean 

 altitude of the summits and crests is greater in limestone ranges 

 than in those of crystalline schists of equal height. In Alpine ranges 

 of similar geological formations this distance becomes far greater 

 when they rise far above 9000 feet (French), where, owing to the 

 formation of steep precipices and summits, and of massive snow-beds 

 and glaciers, the depression of the limit of springs is, comparatively, 

 very considerable ; — 5. The diminution of the temperature in pro- 

 portion to the altitude does not take place in an equal arithmetical or 

 geometrical progression. In the valleys it progresses more slowly 

 than at the declivities and summits ; and cceteris paribus advances 

 more rapidly at higher elevations ; — 6. Almost the same temperature 

 is found at the limits of the growth of trees in the different Alpine 



* Originally communicated to Poggendorf 'a Annal. der Physik u. Chemie. 



