i jo 



SCIEXCE-GOSSIP. 



of my long-cherished ideas of the Wealden fissures 

 gained a supremacy in my mind. I therefore 

 decided to move to Sevenoaks, and give myself up 

 to an inch-by-inch search for fissures, which I felt 

 sure must exist, if our ideas about the oscillation 

 of the Weald surface had any item of fact in them. 

 Xor were either my speculations or my searchings 

 in vain, as ultimately I found the fissures exist all 

 over the area of the hard rocks — from within a few 

 yards of the Channel to the North Downs. But 

 although I soon succeeded in finding what I 

 thought was going to prove a panacea for all the 

 ills of criticism, I was sorely disappointed in 

 digging into them to find no trace of any fossil of 

 any kind. Disappointing and discouraging as this 

 was, it only made me more determined to hunt for 

 further fissures, and work the scanty river-deposits 

 wherever they appeared to present conditions 

 anything like favourable to the preservation of 

 bones and shells. Xow and then my persistence 

 in the latter fluviatile remnants was rewarded by a 

 few bones and some vegetable remains. Un- 

 fortunately, however, these usually turned out to 

 be either specifically indeterminable bones or those 

 of an animal still living, or, perhaps, one not before 

 recorded from pleistocene beds. There was one 

 feature in all the barren fissures that soon struck 

 me, and that was that the top was always open, 

 so that the contents were in free communication 

 with the destructive surface-waters. At last I 

 discovered a quarry in which there were four or 

 five more or less yawning rents, and, lo ! one of 

 them had long since forbidden the admission of 

 the dissolving element. It is this fissure to which 

 I now invite my readers' attention. 



Unfortunately I cannot here go into the history 

 of the Shode upon whose banks these fissures 

 occur, or detail the remarkable, and as yet un- 

 published, evidences of repeated ice-action and 

 arctic conditions furnished in the surrounding 

 district. Suffice to say that upon the counterscarp 

 we have patches of gravel succeeding each other 

 in lines directed towards the Darent Gorge, which 

 were deposited either by that river or its tributaries. 

 The lay of these gravels and their composition, 

 both on the former shoulders of the Shode and the 

 succeeding rivers towards the west, show that the 

 current in each case formerly flowed from south to 

 north. An enormous slipping out of the Wealden 

 clay-wedge from under the greensand escarpment, 

 or a down-throw from another cause, now occurred, 

 by which the river bed at Plaxtol was lowered 

 several hundred feet, thus reversing the direction 

 of the stream. To this bend the yielding gault 

 clay accommodated itself, thereby apparently 

 doubling its outcrop, as did the soft sands of the 

 Folkestone beds. But the hard rocks naturally 

 fissured the w-hole of the distance along the valley. 

 It is only natural to imagine that the waters of the 



river, together with their burdens, should gain 

 access to these fissures and ultimately fill them. 

 Since the time the waters first began to fill these 

 receptacles, the erosive action has worn down the 

 bed of the stream some eighty feet at this spot, and 

 the main stream has dwindled down to about five 

 or six feet wide. An interesting race was then 

 initiated between the eroding away of the river 

 bed with the consequent lowering of the altitude of 

 the waters, and the filling up of the fissures with 

 river debris. In four out of the five cases the 

 filling action was victorious ; but in the fifth, the 

 top of which was more elevated, erosion was 

 the winner, and the highest point the debris-charged 

 waters rose still left a chamber some four or five 

 feet in height unfilled. But now the destructive 

 action of meteoric waters was brought to bear 

 upon the contents of the fissures ; and in those 

 which opened directly upon the surface, the 

 dissolving power of the acid - charged liquid 

 acted so thoroughly that to-day there is not 

 left the vestige of a bone or shell, but in the inter- 

 stices there is a deposit of flocculent lime. In the 

 case of the other fissure the limestone roof offered 

 matter for attack, which was quickly taken up and 

 again re-deposited on the ceiling, walls and floor of 

 the chamber, which thus sealed down the contents 

 of the fissure and preserved them from future 

 destruction. 



Those who are not quite familiar with the 

 nature of the burdens of the drainers of a county 

 are advised to spend a day or two between tide- 

 marks in the lower reaches of a river ; it will 

 doubtless prove a revelation. It is just such a 

 heterogeneous collection as can here be found that 

 filled the Ightham fissures ; and just as one could 

 restore a picture of the life of to-day from the river- 

 deposited mass, so we can restore a picture of the 

 life of the time when the Shode was carrying its 

 burdens into the fissures upon its banks. 



Only faint justice, however, can be done to this 

 subject in the space at my disposal, seeing that the 

 fissure has furnished materials for an almost com- 

 plete monograph of the pleistocene fauna. We 

 must, therefore, be content with an enumeration of 

 species so far as they have been published, and a 

 few general remarks upon the conclusions to be 

 drawn from them. 



List of Fossils from the Ightham Fissures. 



Plant.e. — Hypnum proelongum, Chora, Corylus 

 avellana (gnawed nuts), Quercus robur (acorns). 



Insecta. — Julus, Porcella scaber, Cynips, Otiorhyn- 

 chus, 1 . Chrysomela. 



Ostracoda. — Candona Candida, Mull. 



Mollusca. — Limax maximus, Linn ; Hyalina 

 cellaria, Mull. ; H. alliarius. Mull ; H. crysiallina, 

 Mull. ; H. julva, Mull. ; Helix (Patula) rotundata, 

 Mull. ; H. (Vallonia) pulchella, Mull. ; H. hispida, 



