Correspondence — Mr. T. V. Holmes. 137 



SUBSIDENCES AT BLACKHEATH. 



Sir, — I shall be glad if you can afford space for a few remarks on 

 the letter of the Eev. Osmond Fisher in the current Number of the 

 Geological Magazine. 



Mr. Fisher asks, in the first place, if these subsidences are a new 

 feature at Blackheath. In repl^^ I have to state that, in addition to 

 the three subsidences mentioned in the Eeport of the Subsidence 

 Committee, three others (at least) are known to have occurred 

 within the memory of persons now living, though I am unable to give 

 precise dates. But as two of the three were just outside the limits 

 of the open space at Blackheath, and the third, though on the heath, 

 appeared in the corner of a large and irregularly-worked gravel- 

 pit, about forty-five years ago, none of them excited much attention. 

 The three later subsidences, on the other hand, having all been on 

 the surface of what is practically a great open playground both for 

 children and adults, their appearance caused general alarm. Again, 

 in Charlton Park, little more than a mile E. of Blackheath, and 

 exactly like it in geology and phj'sical geography, subsidences have 

 appeared from time to time. But as Charlton is a private park, they 

 remained quite unknown till Mr. F. C. J. Spurrell read his paper on 

 " Danes' Holes " at the Archeeological Institute last April. It is 

 thus evident that only those subsidences that from their public im- 

 portance have excited public interest have become generally known. 



I do not think the Blackheath pits have any affinity to the Dorset 

 pits mentioned by Mr. Fisher; the latter seem to me — judging from 

 his letter — rather to resemble those at Whitlingham, near Norwich. 

 At Blackheath there is nothing in the appearance of the surface to 

 suggest the operation of any general natural cause. A large portion 

 of its surface is smooth and flat. The rougher ground is occupied 

 either by large disused gravel-pits or by patches of small, shallow, 

 irregular hollows, due apparently to primitive diggings for gravel. 

 Hasted, in his History of Kent, vol. i. (1778), speaks of the high 

 reputation of the Blackheath gravel, which caused it to be sent to 

 great distances. He also remarks that when the rebels under Lord 

 Audley were defeated on Blackheath in 1497, 2000 bodies were 

 buried there, and that their graves are now visible. Pre-existing 

 gravel-pits were doubtless used as graves, and the slow dissolution 

 of the corpses beneath a thin gravel covering might give rise to such 

 hollows. 



Mr. Fisher's paper on the Lexden Pit was pointed out to me a 

 year ago by Mr. F. Eutley, who has given an alternative explanation 

 in the same Vol. (1866) of this Magazine. (By a strange over- 

 sight I only noticed a day or two ago the note referring to the paper 

 on the Dorset pits.) But after carefully reading both explanations 

 of the Lexden pit, the result was — to my mind — to show the diffi- 

 culties in the way of any purely geological explanation ; while, at 

 the same time, no other view seems to have suggested itself either 

 to Mr. Fisher or to Mr. Eutley, who yet differ fundamentally from 

 each other. It was impossible, therefore, for me to have any opinion 

 on the Lexden pit and its bearing — if any — on those at Blackheath. 



