DOMAIN XI. DECOMPOSED. 



compress them. But the external parts, harden- 

 ed by contact with the air, are not susceptible 

 of the same compression. They must then se- 

 parate, and thus form the exfoliations which are 

 observable. 



" This explanation acquires the highest degree 

 of probability, when we see some of these large 

 plates still adhering, above and below, to the 

 layers of which they were a part, and only se- 

 parated in the middle, where they form a kind 

 of convex arch on the external side; and the 

 identity of the substance, as well as the parallel 

 direction of their veins with those of rocks from 

 which they are separated, demonstrate that they 

 have formerly been united with them."* 

 Rapid. The decomposition of these prodigious works 

 of nature, the Alps, is far more rapid and in- 

 cessant than might be supposed, increasing per- 

 haps in proportion to their antiquity. The fol- 

 lowing grand and striking observation of Saus- 

 sure, will not fail to impress the reader with this 

 singular truth : " I do not exaggerate when I 

 say that we did not pass an. hour, without seeing 

 or hearing large masses of rock precipitate them- 

 selves, with the sound of thunder, either from 

 the sides of Mont Blanc, or the Aiguille Marbre, 

 or from the crest on which we stood." j- 



* Sauss. 1748. f 2048. 



