RASAY, GEOLOGY. 



obtain any access to these rocks, and it is seldom safe 

 to remain long where the rising of the wind or sea may 

 prevent the possibility of returning. 



In a gradation from the shale follow the great beds 

 of sandstone, of which the exterior edges are exposed 

 along the eastern shore, forming the great range of 

 mural cliffs already mentioned. It is not possible to 

 obtain any where such access to these beds as to 

 discover by what gradations they change ; but while 

 the whole series is strictly consecutive, slight variations 

 are found in the detached parts, which seem to indicate 

 that they become purer and whiter as they proceed 

 upwards. The direction of the whole must be taken 

 in a general sense as northerly, since it cannot be ac- 

 curately determined; and it is thus similar to that of 

 the red sandstone on which it lies ; its dip, like that 

 of the shale and limestone, being westerly, although no 

 means are any where afforded of ascertaining the angle 

 of inclination. 



By comparing the very moderate dip of these beds 

 with the altitude of the cliffs, it will be seen that there 

 is no great difference between that altitude and their 

 collective thickness ; and as the former may be fairly 

 estimated at 1000 feet, the depth of this mass of strata is 

 evidently very great. 



The general character of the sandstone is argillo- 

 calcareous. It is often of a yellowish colour, but oc- 

 casionally of the purest white ; while towards the lower 

 parts it is contaminated with blue clay, mica, and 

 fragments of shale, containing also carbonized wood 

 and a few of the organic remains already described. 

 Large ammonitge are also found in it, but I did not 

 procure any specimens so perfect as to enable me to 

 ascertain the species ; if indeed it has been described 

 by writers on conchology.* Portions of this rock are 



* The inadmissible expense of engravings adequate to the illustration 

 of these and many similar subjects, must be an apology for their absence. 



