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GEOLOGICAL MEMOIRS. 



Iii the Alps, on account of the vast mass of the mountains and the 

 various inclinations and summits, it becomes very difficult to distin- 

 guish definite "groups" and their laws. Vegetation, also, and culture, 

 and especially the products of weathering, obscure the original form 

 of the district. To correct the errors arising from hence it is highly 

 desirable to examine these valleys at intervals more or less extended, 

 as we were enabled to do in the Tauern Alps and in the Oetz Valley. 



The following researches have especial reference to the crystalline 

 slates of the Upper Alps ; we did not, however, omit to study the 

 characteristic phsenomena of the limestone Alps. And in this we 

 have sought, by our determinations of height, by the comparison of 

 inclinations, and by the execution of numerous profiles, to preserve 

 assured data which may serve to give accurate and well-defined ideas 

 of the characteristic forms. Such special researches are not without 

 value for the general questions of geology. L. von Buch, in his 

 well-known "Researches on Granite and Gneiss," has shown how 

 intimately their external forms are connected with the most im- 

 portant processes that have taken place at their appearance on the 

 earth's surface*. 



Basin-shaped Valleys in the Alps. — In considering the charac- 

 teristic forms of the Alpine valleys, much importance is to be attached 

 to their upper extremities. Here are found peculiar basin-like cavi- 

 ties, which are sometimes occupied by the great Firn-meers, so essen- 

 tial to the existence of glaciers. Such a cavity is known as a " Mulde " 

 (basin) or "Circus," in French Cirque (de neve) ; in many parts of 

 the German Alps it is termed a " Kahr." The great bodies of ice 

 and neve of the glaciers, by the covering up of slight inequalities, 

 are well qualified to exhibit more clearly the character of these circular 

 cavities ; and only interfere with the general features so far as to 

 cause the crests surrounding the basins to appear as naked moun- 

 tains of snow and ice, whilst by closer examination they are found 

 to be regular rock-ridges. These differ considerably in relative ele- 

 vation ; particularly in the hindmost, highest parts, it is often so 

 slight, that only some grotesque, jagged pinnacles form the boun- 

 dary of the basin ; their base is for the most part hidden by the 

 " firn," but their outline is more or less recognizable by means of 

 the bedding of the "firn" and the direction of its crevasses. We 

 have also, at rather lower altitudes, altogether similar forms not 

 covered by snow, which may be compared with them. They are 

 pretty clearly distinguishable from the peculiar "Kessel-" [cauldron- 

 like] valleys, in which the lines of inclination must converge towards 

 a central point. In the alpine basins [Mulden] there is evidently a 

 decided inclination towards the middle in the direction of the trans- 

 verse axis of the two sides ; and we can trace more or less clearly a 

 kind of central axis downward throughout the whole basin. These 

 lines, however, together with the whole basin, have a very constant 

 inclination towards its front entrance. In consequence of the bottom 

 of the valley not being itself horizontal, it happens that on many 

 maps the true form of these valleys can be scarcely recognized, since 

 * Abhand. d. Acad. Berlin fur 1842. 



