416 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [April 26, 



hole in the roof from the stratum of sandstone which lies above the 

 Great Limestone. The decomposed stuff in which the sandstone was 

 embedded contained detached pieces of carbonate of lead. 



The remains of the flat were situated on the north side (h) of this 

 rubbish. It consisted chiefly of impure hydrated oxides of iron 

 mixed with sulphide of lead, partially, and not unfrequently alto- 

 gether, changed into carbonate. The oxide was evidently derived 

 from limestone Avhich had been impregnated with carbonate of iron, 

 as nodules of the latter remained unchanged in the centre of de- 

 tached masses of the oxides. It appears probable that this limestone 

 was ferruginized about the time when the sulphide of lead was de- 

 posited in the flat. SmaU caverns lined with snow-white arragonite 

 occurred in this mass of oxidized matter. 



On the south side of the vein there was an open cavern (c) par- 

 tially filled with broken limestone, not much mineralized with iron. 

 The roof of this cavern was lined with stalactites, and the rough 

 lumps of jagged limestone lying at the bottom were covered with 

 corresponding stalagmites. In one or two small caverns near or in 

 the roof some beautifully branched arragonite was formed upon hard 

 limestone, from which it could not be detached without breaking. 



Below the larger lumps of sandstone, &c., which had fallen into 

 that part of the cavern («), small openings had remained unfilled 

 with the soft clay and rubbish. In these openings arragonite was 

 formed upon the clay ; and in one instance it had shot horizontally 

 across one of the small caverns from the oxides of iron and entered 

 the clay at a, which formed the opposite side of the cavern. The 

 clay was hardened around the place where it was pierced with the 

 arragonite, and small crystals of the latter were formed upon it 

 pointing in an opposite direction. 



From these facts the following inferences may be drawn : — 



1. That the limestone rocks forming the sides of this vein and flat 

 were metamorphosed by agencies of the same kind as those which 

 have effected a similar change upon the limestone strata forming the 

 sides of veins and flats in the Nenthead Mines. 



2. That, after the formation of joints, this Kmestone (partially 

 metamorphosed into carbonate of iron, in which were formed caverns 

 lined with galena and other minerals) was subjected to decomposing 

 agencies, and a large cavern formed, which ultimately was filled with 

 elay and rubbish by the falling in of the roof. 



3. That after the roof had fallen in, stalactites and stalagmites 

 were formed in the cavern (c), all of which were more or less co- 

 loured by chalybeate waters flowing over them ; and in some places 

 crystals of pure white arragonite were formed upon these congealed 

 masses of lime, and also upon clay and impure oxide of iron. 



4. That after the roof had fallen in, the cavern had never been 

 filled with water ; for, had this been the case, the clay would have 

 softened and settled down like a sediment, whereas the contents of 

 the cavern appeared like a mass of rubbish just filled in by a navvy, 

 and clay not unfrequently forming a portion of the sides of the inter- 

 stices between the detached pieces of limestone and sandstone. 



