Vol. 50.] OSSIFEROUS FISSURES NEAR IGHTHAM. 177 



Beds, — or very shortly afterwards, — was flowing from N. to S. as 

 now. Having previously cut through the Folkestone Beds it 

 gained access to the fissures, and began to deposit its sediment in 

 them ; and it continued to do so during the whole period that its 

 waters could carry materials into an unfilled space. Since this 

 work of filling commenced, the river has cut its bed through about 

 85 to 90 feet of solid ' rag ' at this spot. But deepening doubtless 

 went on long after flood-waters reached for the last time the 

 altitude of 300 feet, which was about the limit at which the fissures 

 stopped filling. 



III. Description of the Fissures near Ightham. 



Although there are numerous fissures in the Shode Yalley, I shall 

 confine myself to those on the western side of the promontory pre- 

 viously described. Here a quarry has been worked and a face 80 feet 

 high exposed : the direction of the working is a little W. of X. by 

 a little E. of S., thus revealing the fissures as seen in fig. 4, p. 178. 

 The strike of these is practically at right angles to the direction of 

 the downthrow of the valley. They are entirely in the Hythe Beds, 

 which ar. this place consist of layers of exceptionally hard, slightly 

 sandy, crystalline limestone — the Kentish Rag — alternating with 

 friable, though often somewhat tough, beds of hassock ; the thick- 

 ness of the layers being from 1 to 2 feet for the rag, and 2| to 

 3| feet for the hassock. By the southward depression of the valley 

 previously demonstrated, the beds are brought from a northerly dip 

 to a horizontal position. There is a slight downthrow of about 

 18 inches to the south, the mass between b and c forming a 

 miniature trough fault — a feature characteristic of the kind of 

 earth-movement here und3rgone, the overlying hassock bending 

 over and thickening in accommodating itself to the new conditions. 

 A little farther down the valley the limestones are shown with a 

 decided reversed dip. 



The beds at the top have been very much altered, weathered, 

 broken up, and decomposed for about 4 or 5 feet, and trailed 

 down in the direction of the fall of the surface. It is still visible 

 how the upper parts of fissures a and cl have been bent and trailed 

 down the hill ; cl towards the Shode, and a into the valley of the 

 tributary. As these two fissures, and also c, had obviously been in 

 contact with the surface, I confined my attention chiefly to b ; of 

 this fig. 5 (p. 179) is a generalized vertical section. The width of 

 this fissure is from 1| to 5 feet : when I first saw it, it did not reach 

 the surface by about 4 feet ; there was a ceiling of stalagmite about 

 12 inches thick ; flocculent lime has also been redeposited into the 

 cracks, crevices, and interstices of the grains of the adjacent rocks 

 (shown in the figure by the wavy lines). Below the ceiling was an 

 empty chamber (b) some 4 or 5 feet in height ; the walls and floor 

 were covered by a continuous deposit of lime, chiefly in the form of 

 flos ferri at the sides ; while white, with a slightly yellowish-brown 

 tinge, granular stalagmite covered the bottom, some 3 or 4 inches 



