PROCEEDINGS OF GEOLOGICAL SOCIETIES. 



257 



of a languid temperament, mountains with checked circulations, mountains 

 in nervous fevers, mountains in atrophy and decline. 



This change in the structure of existing rocks is traceable through con- 

 tinuous gradations, so that a black mud or calcareous slime is impercepti- 

 bly modified into a magnificently hard and crystalline substance, enclosing 

 nests of beryl, topaz, and sapphire, and veined with gold. But it cannot 

 be determined how far, or in what localities, these changes are yet arrested ; 

 in the plurality of instances they are evidently yet in progress. It ap- 

 pears rational to suppose that as each rock approaches to its perfect type 

 the change becomes slower ; its perfection being continually neared, but 

 never reached ; its change being liable also to interruption or reversal by 

 new geological phenomena. In the process of this change, rocks expand 

 or contract ; and, in portions, their multitudinous fissures give them a duc- 

 tility or viscosity like that of glacier-ice on a larger scale. So that many 

 formations are best to be conceived as glaciers, or frozen fields of crag, 

 whose depth is to be measured in miles instead of fathoms ; whose cre- 

 vasses are filled with solvent flame, with vapour, with gelatinous flint, or 

 with crystallizing elements of mingled natures ; the whole mass changing 

 its dimensions and flowing into new channels, though by gradations which 

 cannot be measured, and in periods of time of which human life forms no 

 appreciable unit. 



II. Formation. — Mountains are to be arranged, with respect to their 

 structure, under two great classes — those which are cut out of the beds of 

 which they are composed, and those which are formed by the convolution 

 or contortion of the beds themselves. The Savoy mountains are chiefly 

 of this latter class. When stratified formations are contorted, it is usually 

 either by pressure from below, which raises one part of the formation above 

 the rest ; or by lateral pressure, which reduces the whole formation into a 

 series of waves. The ascending pressure may be limited in its sphere of 

 operation ; the lateral one necessarily affects extensive tracts of country, 

 and the eminences it produces vanish only by degrees, like the waves left 

 in the wake of a ship. The Savoy mountains have undergone both these 

 kinds of violence in very complex modes and at different periods, so that 

 it becomes almost impossible to trace separately and completely the opera- 

 tion of any given force at a given point. 



The speaker's intention was to have analysed, as far as possible, the ac- 

 tion of the forming forces in one wave of simple elevation, the Mont Sa- 

 leve ; and in another of lateral compression, the Mont Brezon : but the 

 investigation of the Mont Saleve had presented unexpected difficulty. Its 

 facade had been always considered to be formed by vertical beds, raised 

 into that position during the Tertiary periods ; Mr. Huskin's investigations 

 had, on the contrary, led him to conclude that the appearance of vertical 

 beds was owing to a peculiarly sharp and distinct cleavage, at right angles 

 with the beds, but nearly parallel to their strike, elsewhere similarly mani- 

 fested in the Jurassic series of Savoy, and showing itself on the fronts of 

 most of the precipices formed of that rock. The attention of geologists 

 was invited to the determination of this question. 



The compressed wave of the Brezon, more complex in arrangement, was 

 more clearly defined. A section of it was given, showing the reversed po- 

 sition of the Hippurite limestone in the summit and lower precipices. This 

 limestone-wave was shown to be one of a great series, running parallel 

 with the Alps, and constituting an undulatory district, chiefly composed of 

 chalk beds, separated from the higher limestone-district of the Jura and 

 Lias by a long trench or moat, filled with members of the Tertiary series — 

 chiefly nummulite limestones and flysch. This trench might be followed 



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