256 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Mar. 1 9, 



meet with deposits having the same characters, and apparently be- 

 longing to the same age, at and about Mauchline in Ayrshire ; and, 

 if we add this to the number, it gives us either six or eight patches 

 of sandstones, covering several widely remote areas in the South of 

 Scotland. 



Physical Geology of the Sandstone-areas. — Besides the question 

 as to the geological age of these patches, their position and isolation 

 are matters of some importance, and there are certain circumstances 

 connected with the physical geology of these strata which render 

 them interesting. 



As the Dumfries area has been already described, any matters of 

 detail connected with this may be found in the memoir already 

 alluded to. There are, however, certain phenomena or physical 

 characters which . are not there mentioned, and which should be 

 noticed. 



Corncockle Sandstone-area. — To commence with the Corncockle 

 area, — this presents us with sandstones and breccias, but they have not 

 the same relative arrangement as deposits of this nature have in the 

 district around Dumfries. In the latter area we have a considerable 

 thickness of sandstones, forming the lower portion of the deposits ; 

 these are succeeded by thick breccias (Craigs breccias) ; and above 

 all we have sandstones, which are not extensively developed (Castle- 

 dikes sandstone). In the Corncockle area there appear to be no equi- 

 valents of the breccias, nor the higher-lying sandstones ; and the same 

 remark, so far as I can ascertain, applies to all the other areas both 

 in Dumfriesshire and Ayrshire. Breccias do occur in the other areas, 

 but not under such circumstances as are presented in the Dumfries 

 district. 



In the most southern portion of the Corncockle area, at Dalton 

 Hook, we have breccias exposed ; and these possess some features 

 which are peculiar in Dumfriesshire. Here they were formerly 

 wrought for lime ; the calcareous matter occurring in the form of 

 angular fragments of Carboniferous Limestone, characterized by the 

 usual fossils : these angular fragments are associated with others de- 

 rived from the Lower Silurians. Both the Carboniferous and the 

 Lower Silurian formations are met with at about a quarter of a mile 

 from the spot where this breccia has been worked. In this locality 

 the strata dip N.N.W., at a slight angle. 



Breccias of a somewhat similar nature are seen in the course of 

 the Water of Milk, about two miles east from Dalton Hook ; and at 

 the northern end of the Lockerby railway-cutting the breccia also 

 makes its appearance ; but here the fragments seem to be exclusively 

 of Lower Silurian origin, and the inclination is more towards the west. 

 Beds of sandstone are met with in the course of the Dryffe Water ; 

 and in the small burn which runs from the N.E. near Nether Cleugh 

 station, on the Caledonian Railway, beds of a similar nature are like- 

 wise found. In the course of the Upper-Cleugh Burn, immediately 

 as the newer beds come in contact with the Lower Silurians, the 

 former assume a brecciated character, like the deposit which is seen 

 at the north end of the Lockerby Cutting ; but at Upper Cleugh the 



