512 



EET. J. P. BLAKE ON THE 



Fig. 19. — Section looMng norih^ Car eg Givladys, 



2 13 2 1 



1. Limestone, with slate-fragments. 2. Purple and green ashes and slates. 

 3. Eedder ditto. 



reddened, and looks shaly. In the same line, further south, are 

 some bedded-looking calcite-roeks. Further still to the south, 

 another boss, when looked at from the east, shows a large mass of 

 calcite running irregularly and in strings amongst the ashes, which 

 are also reddened in its neighbourhood. In the same boss, on the 

 southern side, is a curious quartz-knob, of smaU size, ending upwards 

 in a swelling, like the handle of an umbrella, and having the ashes 

 or shales clinging round it. These intrusive-looking limestones are, 

 in a certain sense, also calcareous breccias, since imbedded in them 

 there are larger and smaller fragments of red shale up to one or two 

 inches in diameter. 



In attempting to account for these phenomena we can scarcely 

 look to an organic origin for the limestone in its present state, and 

 certainly not for the quartz. The crystals must have been formed 

 from solution in water. In the case of the breccia, the fragments 

 of which are not in the least arranged in bands, unless these were 

 ejected volcanically, there must have been motion in the water. 

 Any supposed folding of the beds which should produce the appear- 

 ance of fig. 19 would be most extraordinary, and difficult to imagine 

 in face of the uncontorted character of the blue slates. The only 

 method by which I can explain the circumstances is to consider the 

 limestones the product of calcareous springs, as I consider the quartz- 

 knobs to be the result of siliceous ones. The red colouring is pro- 

 duced by oxidation in contact with the oxygen-carrying water. 

 The fragments fall from the roof, or are broken off, and come at 

 last to be imbedded where the precipitation takes place. If the 

 final precipitation is external, we may have bedded limestones in 

 which it would not be impossible to find organisms ; if internal, 

 the limestones wiU take curious forms according to the shape of the 

 fissures which the water depositing them may be able to make. 

 There is no reason why some of these bedded limestones may not be 

 of great extent, like the travertines of Rome. 



There are, in fact, in this very spot large masses besides those 

 already described. Among the sand hills, to the east of the cliff, 



