AILSA. GEOLOGY. 495 



blende collected in small groups and condensed towards 

 a central point. It adds another variety to the list of 

 those rocks which, like basalt, are capable of assuming 

 a columnar form. Numerous trap veins traverse this 

 rock. They are of considerable dimensions, and from 

 the abrupt form? of the cliffs, expose their courses for 

 a great space ; presenting this geological fact in a very 

 interesting view. The greater number are vertical, or 

 at least highly erect, and they are attended with no 

 disturbance or derangenlent of the surrounding rocks 

 beyond that of simple separation ; nor is there any 

 alteration of either rock visible at the planes of contact. 

 Having so often noticed the picturesque scenes that 

 have occurred in the different places described throughout 

 this work, objects which have conduced to alleviate 

 the toils and inconveniences that must attend every 

 voyage through a climate so precarious, and a region 

 so stormy, it would be unpardonable to conclude the 

 description of the islands of the Clyde, without pointing 

 out the extreme beauty of this river, from Dumbarton 

 to its gradual and final termination in the open sea. 

 The shores of the western boundary are every where 

 characterized by cultivation, by woods, scattered trees, 

 towns, and villas ; displaying, with all the marks of 

 wealth and high population, innumerable scenes of pic- 

 turesque effect. On the opposite coast, the mountains 

 of Argyllshire present the reverse character, that of 

 wildness ; the sea margin being still skirted by occasional 

 patches of natural wood, and ornamented by the houses 

 of the opulent proprietors. On this side, the intricate 

 inlets of Loch Long, Loch Fyne, the Gare Loch, and 

 numerous others, will conduct the traveller to all the 

 varieties of mountain scenery which Argyllshire affords 

 in perfection ; these being occasionally further diversified 

 by the castles of ancient times. Those narrow straits 

 are often peculiarly striking from the height of the 

 land immediately enclosing them, and from the pictu- 



