242 Elie de Beaumont's Researches o?i some of 



naturally carries with it the idea of horizontality, that it is never 

 without surprise we first hear of sedimentary beds observed 

 in a vertical or nearly vertical position. 



As early as 1667, Stenon maintained that all inclined sedi- 

 mentary beds were upraised ; and since the observations of 

 De Saussure on the Valorsine conglomerates, geologists have 

 generally agreed in considering those sedimentary beds which 

 are frequently observed in mountainous countries either in- 

 clined at considerable angles, placed vertically, or even thrown 

 over, as not having been formed in that position, but as having 

 been so circumstanced, in consequence of phaenomena which 

 have taken place at a greater or less time after their original 

 deposition. 



There are few countries where these phaenomena have been 

 produced at so late a period, as to affect all the sedimentary 

 deposits there existing, even abstracting the alluvion of modern 

 rivers, which in all cases has not yet been disturbed by any 

 phaenomena of this nature. 



We observe along nearly all mountain chains, when we at- 

 tentively examine them, that the most recent rocks extend 

 horizontally up to the foot of such chains, as we should expect 

 would be the case if they were deposited in seas or lakes of 

 which these mountains have partly formed the shores ; whilst 

 the other sedimentary beds tilted up, and more or less con- 

 torted on the flanks of the mountains, rise in certain points 

 even to their highest crests. Thus in each chain, or rather 

 in each system of chains, the series of the sedimentary rocks 

 is divided into two distinct classes, and the point of separation 

 of these two classes, variable from one system to another, is 

 one of the circumstances which best characterizes each parti- 

 cular system. 



At the same time that the position of the ancient and in- 

 clined beds furnishes the best proof of the elevation of the 

 mountains of which they constitute a part, the geological age 

 of these beds affords the best means of determining the rela- 

 tive age of the mountains themselves ; for it is evident, the 

 first appearance of the chain itself is necessaril}' intermediate 

 between the period when the beds, now upraised, were depo- 

 sited, and that when the strata were produced horizontally at 

 its feet. 



There is nothing so essential to remark, as the constant 

 clear line of separation between these two series of beds in 

 each chain. This kind of observation is sanctioned b}' long 

 experience. Geologists have, in fact, been long accustomed to 

 employ the absence of parallelism in the sti-atification of two 

 systems of beds, the one supporting the other, as affording 



the 



