36 



generally throughout the district are similar to those often described 

 in connection with the contact of the trap rocks and the sedi- 

 mentary strata. Some very peculiar effects will be described 

 farther on. 



V. THE OLD BED SANDSTONE AND ITS LIMESTONES. 



27. In addition to what has been already said regarding this rock 

 as a base to the carboniferous formations, we have now only to 

 notice those portions of it which appear upon the shores of the frith. 

 Those on the north are prolongations of the Kilpatrick hills, which, 

 subsiding at the valley of the Leven, rise again to much lower 

 altitudes in a ridge bounding the Clyde on the north as far as the 

 shores of Gareloch. Thence the old red sandstone passes into the 

 peninsula of Roseneath, in which its junction with the underlying 

 old slates is strikingly marked on the features of the landscape.* 

 It crosses nearly through the middle of the remarkable and very 

 picturesque dell, which intersects the peninsula from Campsail Bay 

 to Kilcreggan in a direction nearly north-east and south-west. 

 Thus, in external aspect, and in the nature of its rocks, this southern 

 portion is isolated from the rest ; it consists of a single hill of a 

 depressed conical form, having a smooth outline, and extending in 

 gentle and fertile slopes to the water's edge on three sides. Here, 

 as in other places, the soil formed by the decomposition of the 

 sandstone contrasts most favourably with that which rests upon the 

 cold retentive clays of the coal formation on the one side, and the 

 old slate rocks on the other. The series exhibits but its lowest 

 members conglomerates, coarse sandstone and finely laminated 

 red sand, irregularly disposed. The base of the conglomerate is 

 coarse red sand ; and the imbedded fragments are granite, porphyry 

 quartz, and various kinds of slate ; the three former are very much 

 rounded, the latter have lost their angularity, and present elliptic 

 forms. The origin of these is to be looked for in some near district 

 of the Grampians, where such varieties exist, and which we know 

 were elevated and exposed to the action of mechanical forces prior 

 to the epoch of the old red sandstone ; the quartz and slate pebbles 

 are from the adjoining strata. 



The contact of the sandstone and slate is nowhere seen. In the 

 western part of the cliffs at Portkill Bay, the two rocks approach 



* "Rosencath" is said by some to mean in the Gaelic language, "the little dell, or 

 dingle ;" and that the name was given to the whole from this peculiar feature. See 

 Ncic Statistical Account tinder " Roseneath Parish, Dumbartonshire,'' 



