Correspotidence — F. J. Bennett. 573 



THE LOOSE VALLEY, ETC., NEAR MAIDSTONE. 

 Valleys of subsidence initiated by Swallow-holes. 



Sir, — My attention has for some time been called to the formation 

 of valleys from what seems to me a new point of view, and both at 

 and near Mailing the evidence for this seems as clear as one can 

 expect in these cases. 



This evidence seeins to point that these valleys, all of which are 

 in the same formation, viz. the Hythe Beds, and I would also 

 include some valleys in the Chalk, have been initiated by swallow- 

 holes, and that these have been in their primary stage formed from 

 heloio, by the uprise of the water up lines of weakness imder hydro- 

 static pressure. 



Many of these swallow-holes still exist parallel with the course 

 of the valley, but high and dry, and many of these are known by 

 local names as Jacob's Hole, Baldwin's Hole, etc. Some still contain 

 water, and are situated at the heads of some of the side valleys and 

 are fed by springs. 



It appears also that much more has been done by way of 

 erosion by the invisible underground stream than by the visible 

 one, and the shape of the valley sides, very steep in places, indicates 

 subsidence consequent on the giving way of the valley under the 

 weight above, rather than by subaerial action alone, though this of 

 course has contributed. 



In the case of Loose Valley we have instances of the loss of the 

 stream for over a quarter and half a mile respectively, not an 

 unusual occurrence in limestone areas, but here accompanied by 

 what, as far as I know, is a most unusual feature, viz., that the loss 

 of the valley accompanies the loss of the stream, and that where this 

 occurs the valley ceases practically to exist, and is bridged over. 

 Another governing factor seems to be the varying proportion of the 

 Kag to the soft Hassock, as where the valley ceases there the 

 Hassock is very thin and there the quarries occur, naturally at the 

 place where the Eag is thicker. 



Another interesting feature is the fact that there are various water- 

 levels in this valley, and one case is that of a spring pond at a much 

 higher level than the river and running over into it, a phase in the 

 former state of that valley when this pond was a deep swallow- 

 hole. Again, too, there occur many natural pools along the course 

 of the river, and where these occur the valley assumes a crater- 

 shaped form as if these pools also had once been deep swallow- 

 holes, now worn away. That the loss of the river and of the 

 valley must have escaped notice when the geological map was made, 

 is shown by the fact that at the part where the last issue of the 

 river takes place at the foot of the rise which there terminates the 

 valley, a fault has been mapped, cutting off the Atherfield Clay, 

 which it appears merely passes under that rise. 



But I think I have said enough to show that both the Loose and 

 the Mailing Valleys deserve attention from all those interested in 

 valley formation. F, J. Bennett. 



"West Mailing. 



October 3rd, 1906. 



