212 ANNUAL OF SCIENTIFIC DISCOVERY. 



mountains are at different periods in different stages of health (so to 

 call it) or disease. We have mountains of a languid temperament, 

 mountains with checked circulations, mountains in nervous fevers, 

 mountains in atrophy and decline. This change in the structure of ex- 

 isting rocks is traceable through continuous gradations, so that a black 

 mud or calcareous slime is imperceptibly modified into a magnificently 

 hard and crystalline substance, enclosing nests of beryl, topaz, and sap- 

 phire, 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 appears 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 crevasses are filled with solvent flame, with vapor, with gelatin- 

 ous 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. 



2. 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 con- 

 volution or contortion of the beds themselves. The Savoy Mountains 

 are chiefly of this latter class. When stratified formations are contort- 

 ed, 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 van- 

 ish 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 im- 

 possible to trace separately and completely the operation of any given 

 force at a given point. The speaker's intention was to have analyzed 

 as far as possible, the action of the forming forces in one wave of sim- 

 ple elevation, the Mont Saleve ; and in another of lateral compression, 

 the Mont Brezon ; but the investigation of the Mont Saleve had pre- 

 sented unexpected difficulty. Its facade had been always considered 

 to be formed by vertical beds, raised into that position during the terti- 

 ary periods ; the speaker's investigations had, on the contrary, led him 

 to conclude that the appearance of vertical beds was owing to a pecul- 

 iarly sharp and distinct cleavage, at right angles with the beds, but 

 nearly parallel to their strike, elsewhere similarly manifested 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 position of the Hippurite 



