560 TRANSACTIONS OF SECTION C. 



prove that many, if not all, of the deeper pot-holes owe their existence to 

 faults. Rift Pot, a pot-hole on the south-east side of the hill, was recently ex- 

 plored and found to extend to a depth of over 300 feet : the first portion consists 

 of a vertical shaft 114 feet deep, the lower portion of which consists of a chamber 

 130 feet long and 25 feet broad ; from the south end of this the pot descends for a 

 distance of about 200 feet with a series of platforms of jambed stones wedged be- 

 tweea the walls of a vertical fissure, finally ending in a short passage which at the 

 end is waterlogged. The pot-hole at the surface takes the form of a fissure 60 feet 

 long and from 1 to 7 feet wide. At the northern end of this fissure, within a 

 few feet of the moor level, the east wall is slickensided, and in the main chamber 

 at the foot of the first shaft the east wall is also slickensided over an area 50 feet 

 in length and at least 20 feet in height. At the surface the slickensides occur 

 along successive master-joints while those in the main chamber occur along another 

 master-joint at a horizontal distance of about 15 feet. These .slickensides are 

 horizontal, showing that the fault was one of horizontal displacement, and as a 

 careful examination shows that the beds of limestone on eitlier side of the upper 

 part of the pot correspond, it is clear that no vertical movement accompanied the 

 faulting. The slickensides near the surface are coated with clear crystals of calcite 

 which when removed leave the slickensides very clearly marked. 



Only one fault is marked on the maps of the Geological Survey : this is a fault 

 which runs from near Ilorton to God's Bridge, in Chapel-le-Uale. Along the line of 

 this fault are several pot-holes, all of which have their longer axes in the direction 

 of the fault. Sulber Pot, which is about 59 feet deep, and Nick Pot, which receives 

 an inflowing stream, and has recently been explored to a depth of about 80 feet, 

 exhibit no direct evidences of faulting ; but Mere Gill, on the other hand, does. 

 Mere Gill consists of a fissure, about 80 yards lo7ig, which is bridged in three 

 places by rock. Asa rule this fissure is filled with water to within 30 feet of the 

 surl'ace ; in times of normal rainfall the water escapes through a tunnel below the 

 water-level which leads in a southerly direction (away from the valley) ; it then 

 makes two vertical descents of 80 feet each and turns northwards to emerge in 

 the valley near God's Bridge in the direct line of the fault. On the limestone, 

 which is usually covered by the stream falling into the pot, are crystals of calcite. 

 These are very much water-worn, but clearly indicate the existence of a fault. 



Gaping Gill consists of a vertical shaft, 365 feet deep, into which the waters of 

 Fell Beck fall. At a depth of about 100 feet is a ledge some ll' feet wide : at this 

 point a fault is very clearly to be seen; the fault has a downthrow of feet to 

 tlie south. The shape of practically all the pot-holes is a further indication that 

 they have been formed as the result of faults : they are all much longer than they 

 are wide and thin out at each end into a narrow crack. It is also a noticeable fact 

 that they occur in groups and in such positions that it would have been impos.sible 

 for a stream to form more than one out of several. 



7. Notes on the Speeton Ammonites. By C. G. Danfoijd. 



A residence of several years in the neighbourhood of Speeton lias enabled tlio 

 author to collect many fossils from the clays and shales underlying the Chalk. 

 With regard to the Amnioiiitidcs, his results confirm the general succession given 

 by Pavlow and Lamplugh, and add some further information. 



The lowest portion of the Kimmeridge clay which the author has been able to 

 examine in exposures on the shore contains numbers of ill-preserved ammonites of 

 the square-backed Hoplites group ; while the higher part contains forms of a 

 different type, belonging to the round-baclied Perisphinctes and allied genera. 



In the lower part of the zone of Belemnites lateralis ammonites are extremely 

 rare, and the author has no fresh information to offer; but in the upper pat't they 

 become plentiful. The very globose forms of Olcostephanus (Olc. f/ravesi/ormis, 

 Xei/serlitiffi, &c.) occur mainly in the bed D 3 of Mr. Lamplugh's classification, but 

 are usually in bad preservation. The overlying bed, D 2, is perhaps the most interest- 

 ing of the whole series; at its base both the Olcostejj/tani and the I[oj)lites enn 



