KIRKBY SANDPIPES IN MAGNESIAN LIMESTONE OF DURHAM. 331 



where the pipes are very nnmeroiis, the limestone is more of a slaty 

 nature, though thicker beds of a crystalline and concretionary 

 character are associated. Some of the beds are finely laminated, and 

 a few are soft and marly. 



Some of the pipes begin in rubble overlying the solid beds on the 

 south-west of the quarry, and a few small ones about two feet in 

 length are solely excavated in it. The rubble only exists in this 

 region, where the uppermost beds of limestone seem to have been 

 completely broken up, and all signs of their stratification destroyed, 

 by a disturbance of which further traces are still visible in a broken 

 syncline a Httle beyond the most westerly pipes. The pipes shown 



Lign. 6.— Section of Pipes in Ruljble, near the Slope of a Syncline. 

 e. Sand, clay, and soil (the sand thinning out here) ; g, Thin bedded limestone, much fissured 

 and broken to the west ; g', rubble. 



in fig. 6, which are close to the syncline, are altogether in rubble. 

 The form of the pipes in such loose materials seem to be just as well 

 preserved as when the substance pierced is unbroken. 



These are about all the facts that it seems necessary to notice in 

 describing the pipes ; and so much has been said on the origin of 

 sand- and gravel-pipes by the various authors who have studied and 

 written on those in the chalk, and being perfectly satisfied that those 

 in the magnesian limestone have been similarly originated, that it is 

 scarcely necessary for me to go far into the question, though it may, 

 perhaps, be necessary to draw attention to the theories broached, and 



