190 SYSTEMS OF UPHEAVAL. 



these chains, strata of the same age are found everywhere uptilted, and that 

 the succeeding ones are horizontal. It follows from this circumstance that 

 an upheaval does not take place purely on a mathematical line, but on a 

 band of formations more or less wide, on which it is manifested by several 

 parallel ridges. The same line does not continue always from one end to 

 the other, but we find here and there high and low parts, and those which 

 are concealed by subsequent deposits ; therefore, it is the common line of 

 all the elevated ridges which must be taken for the general direction or 

 ptrike (The word strike is formed from the German streichen, to stretsh, 

 to extend). 



20. The assemblage of directions on the same line, and paral- 

 lel directions, form what is called a system of upheaval, which is 

 synonymous with the expressions, system of fractures, system of 

 uptilted beds, and even system of mountains, although in a more 

 restricted sense than in geography. To designate the different 

 systems, the names of places in which each system is particularly 

 developed have been borrowed ; we say, system of the Pyrenees, 

 system of the Western Alps, &c. 



The great catastrophes which have successively occurred on the surface 

 of the globe appear to have always taken place suddenly. At greater or less 

 distances from places where the stratification is unconformable, we often find 

 the same deposits in conformable stratification, and even joined to each 

 other by a gradual passage ; hence, it follows that deposition has not been 

 suspended, but the movement of the soil has been local over a more or less 

 considerable space of the terrestrial surface, and the interval during which 

 it took place must have been extremely short. This is clearly seen, foi 

 example, at the period of the system of the Rhine, in which the vosgean 

 sandstone is found upheaved, without the bunter sandstein having partici 

 pated in the action ; and, nevertheless, at a short distance the two arena', 

 ceous deposits, where their stratification is conformable, are so joined to 

 each other, that it cannot be determined where one begins or the other ends. 

 The same is the case with the creta'ceous formations; if their different 

 deposits are dislocated in a certain direction, they are conformable for great 

 extents, and they then pass from one to the other in such a manner that 

 they were for a long time confounded as a single formation. 



Submerged and uncovered formations. Sedimentary beds found resting 

 horizontally on the sides of mountains, show that the sea beat against 

 escarpments by deposits upheaved in an anterior epoch; hence the expres- 

 sion of the sea of this or that formation, as the creta'ceous sea, the jura's sic. 

 sea, &c., which indicate the waters beneath which each of these sedi. 

 mentary deposits was formed. When a deposit is wanting in a certain 

 extent of formation, we shonld infer the formation was then above the sea 

 of the epoch, and formed there a more or less elevated island or continent ; 

 thus, at the time when the Parisian limestone was formed, a great part of 

 France, and indeed of Europe, must have been dry, as we scarcely see 

 traces of these deposits anywhere except in the neighbourhood of Paris or 

 Bordeaux. But it also happens that the deposits which we must regard 

 as having been dry at a certain time, were afterwards covered by marine 

 sediment, more modern than the preceding ; and hence we must conclude 

 that, although uncovered prior to the anterior formation, they must have 

 afterwards sunk to receive new deposits: such sinkings make certain catas- 

 trophes particularly remarkable. 



20. What is meant by "system of upheaval"? What is meant by ere- 

 l Cfous sea ? How are the several systems of upheaval classed ? 



