AGT?1CULTURAL MUSEUM ^91 



arches, because, from its undulating surface it is not so 

 w-ell calculate c! to retail them. From this circumstauce, 

 also the siliceous jjarticles abound more on the surface. 

 The stones or gravel wiiich form a large portion of this 

 soil, increases in size the higlier you ascend the rivers. 

 The grave! of the lower dividing ridge of this second 

 shelf, is very fine ; ten miles hig'her up, it is perceptibly 

 coarser. As you approach the head of tide water, stones 

 of a considerable size are found. — These stones and era- 

 vel are formed, as 1 apprehend, partly from the frag^ 

 ments of rocks that are ttirnaway by the torrents, and 

 arc broken, divided and subdivided, and I'ounded off as 

 tiiey are rolled along, crowded together in the bottoms 

 of streams and rivers, until they arrive at ihe places in 

 %vhich they become iixcd : the further they are carried, 

 fhe more are they broken, and the more is their size di- 

 jniiiished. The liner jiarticlss or du-t, which is -detached 

 by this continual rubbing and washing, is carried to the 

 ocean, where if serves to foi-m the pebbles that are cast 

 back by the waves upon the shores. Another part is 

 formed by the affinities of the siliceous particles that 

 com!)ose so large a portion of this region. The more 

 ancient the soil, the more time has there been for the 

 operation of the great laws of composition, and the h>r- 

 gei- are the products. This increase in the size of the 

 stones the higher you ascend the land, seems wisely in- 

 tended by providence, to preserve the moisture of high 

 lands which would be too much exhausted for the purpo- 

 ses of vegetation, by reason of its general unevenness and 

 elevation, were it not for the retentive properties of its 

 stones. 



It also may be remarked of the marls which are found 

 in this region, that the dif^position to turn to lime-stone 

 increases the higher you ascend, though they very rarely 

 shew themselves on the siu'face. but may be occasional- 

 ly observed in baiiks that have been won by streams 



Before we proceed to the description of the next 

 grand region^ it may be useful to recapitulate the subdivi- 

 pions of the alluvial region, to wit: 1'he tiiAt stouclcss^i*' 

 ^ud the undulating or ^ill-c^iou^. 



