THE CLYDE ISLANDS. 507 



insular character of the detached portions which consti- 

 tute the islands. That cause has at any rate been modi- 

 fied by posterior waste, and beyond that it is unnecessary 

 to pursue this inquiry. 



With respect to that part of this sestuary which lies to the 

 north of the Garroch head, the same general reasoning 

 may be applied, although this portion occupies a much 

 smaller space. Here, it is true, the water lies, rather more 

 decidedly, in a cavity of the sandstone, as that rock is 

 found on both sides, although on the northern, inter- 

 ruptedly. At present however, whatever the former 

 actions of the Clyde may have been, that river is employed 

 in filling up the vacuity, not in deepening it. The 

 alluvia brought down from the hills by the powerful 

 streams which form this river, are fast extending the flat 

 land at the point where it meets the sea ; narrowing the 

 navigation, shoaling the water far below Dumbarton, and 

 laying the foundation of future meadows. The time will 

 probably hereafter arrive, when the Clyde, like the Tay, 

 will have filled up the whole tract to the north of Bute, 

 and when the sea lochs included within this space will 

 have become fresh ; discharging their several rivers through 

 the alluvial plains which will then separate them from the 

 ocean. 



