436 THE LANDSLIP AT CLAXHEUGH. 



conditions. In the paper just referred to I proved that this 

 was due to their removal subsequent to deposition, and that 

 .there had existed a cavern between the Yellow Sands and 

 upper Magnesian Limestone along the eastern part of 

 Claxheugh. This underground cavern had subsequently 

 closed up, the limestone settling down on an irregular surface 

 of the Yellow' Sands ; and at the same time many large and 

 prominent fissures were caused in the upper compact lime- 

 stone, due to the consequent strain produced by these move- 

 ments. The nature of the section and the position of the 

 cracks are clearly shown in the accompanying section. 



The cracks are of interest in connection with the landslip, 

 as they have determined the chief features of it. The portion 

 of the upper rock that has fallen is bounded by the two 

 fissures C i and C 2, and was thus situated immediately above 

 the most interesting portion of the whole section. The debris, 

 which amounts to over 600 tons, has thus covered up the 

 peculiar exposures which showed the termination of the 

 Marl Slate and Yellow Sands ; and indeed has, at any rate 

 for the time being, obliterated the evidence from which the 

 existence of the cavern was deduced. Photographs and a 

 section of the manner in which these strata ended will be 

 found in my former paper on Claxheugh. The debris has also 

 covered up the Yellow Sands lying along the foot of the 

 section, blocked up the road that runs along the base, and 

 spread far out over the haugh of the river Wear. The land- 

 slip is primarily due to the unequal denudation of the strata 

 exposed, the Yellow Sands having been continuously cut 

 away and the prominent crag of Magnesian Limestone 

 formed, but the influence of this work has been considerably 

 augmented by the existence of the fissures in the upper rock, 

 caused by the falling in of the top of the cavern, and thus the 

 main features of the landslip were predicted. 



