Vol. 67.] PERMIAN TO THE TRIAS IN NOTTINGHAMSHIRE. 93 



unconformity between the two is a striking one, and pebbles of 

 the eroded Lower Mottled can be found in the Pebble Beds above. 

 The unconformity disappears within a mile on either side of the 

 sand-pit. It seems probable that such a local break would be 

 more likely to occur during deposition at the mouth of a river, 

 rather than elsewhere. 



(/) The Area between Mansfield and Warsop. 



Proceeding northwards from Mansfield, although the base of the 

 Lower Mottled Sandstone is seen to contain many lcnticles of Marl, 

 there is no appearance of a distinct band of marl between the Lime- 

 stone and the Bunter until Mansfield Woodhouse is reached. Here, 

 however, the Marl reappears, and has been traced as far north as 

 Warsop Station, at which point the 6-inch mapping terminated. 

 A large outlier of Marl, not previously known, exists at Park Hall 

 and ]S T ettleworth Manor. 



Before leaving this district, mention must be made of the 

 characters of the Magnesian Limestone. To the north of Sutton- 

 in-Ashfield (as has been already stated) the Limestone increases 

 greatly in thickness, and becomes very variable in composition. 

 The famous dolomite which was used in the foundations of the 

 Houses of Parliament is said to have been quarried at Mansfield 

 Woodhouse. Here it occurs as domes, which form hills, rising like 

 islands from the surrounding flat of normal, flaggy, coarse-grained 

 dolomite. The building-stone is a creamy dolomite of fine texture, 

 without any trace of bedding. The mass is divided up into short 

 thick lenticles, by planes which have no special orientation. A 

 further remarkable feature is the presence of cylindrical cavities 

 known as ' gulls,' which may have a diameter of over an inch with 

 a length of several feet, and lie in any direction. They bear a 

 curious resemblance to the holes made by a crowbar for blasting, 

 and, in fact, when their direction happens to be suitable, they are 

 utilized for the purpose. The appearance of the rock suggests 

 swelling as the result of chemical changes. Although the actual 

 junction of the two varieties of dolomite is not visible, they may be 

 seen in quarries within about 200 yards of one another ; and it is 

 noticeable that the normal flaggy type shows no sign of an on- 

 coming change, nor is its low dip disturbed. 



(2) North Nottinghamshire. 



I have not been able to continue the detailed mapping beyond 

 Warsop Station, but the Permian outcrop has been followed along 

 its entire length to its termination in Northumberland, special 

 attention being paid to published sections. 



At Warsop, superficial deposits mark the junction of the Permian 

 with the Bunter, and the presence or absence of the Permian Marl 

 can only be inferred. However, a section, described and figured by 



