76 REPORT— 1839. 



streamlets flowed in the same direction. From the gradual passage of 

 flag-stone into the massive building-stone, it is argued that the former 

 has never been under much pressure in the upper part, and therefore 

 has always maintained nearly the same distance from the surface that 

 it now has. 



On the Action of Acidulated Waters on the surface of the Chalk near 

 Gravesend. By the Rev. W, Buckland, D.D.,F.R.S.,F.G.S., ^c. 



The author first adverted to the frequency of caves in connexion 

 with fissures in the limestone rocks of all countries ; and considered 

 the enlargement of many fissures into caverns to be due to the cor- 

 roding action of acidulated vapours and waters. He cited a remark- 

 able example of a very lofty dome-shaped cavern at Pantalica, near 

 Syracuse, which he considered to have been produced in this manner. 



He also attributed to the corroding action of water charged with 

 carbonic acid, the origin of the deep irregular furrows, pits, and gul- 

 lies which are so frequently found on the surface of the chalk, and are 

 usually filled with gravel mixed with clay and sand ; and cited exam- 

 ples of excavations of this kind in deep sections of the chalk hills by 

 the road-side between Beaconsfield and High Wycombe, and at the top 

 of the hill immediately east of Henley in Oxfordshire. He refers to 

 the epoch of the plastic clay formation the gravel and clay filling these 

 cavities near Beaconsfield. Here remains of tortoises were found in 

 the clay by the late Lord Grenville. 



About ten years ago a remarkable opportunity occurred at Graves- 

 end of seeing a large surface of chalk stripped of its covering of sand 

 and gravel, and exposing the condition it had acquired before the ar- 

 rival of this covering, which was removed in order to get access to 

 the chalk. Before the deposition of this sand, in which were many 

 bones of deer and other mammals, a shallow bason, about twenty-five 

 feet deep, and extending over a quarter of an acre, appears to have 

 been formed on the surface of the chalk; the entire bottom of this 

 bason presented a surface covered with irregular bowl-shaped cavities, 

 separated from one another by intermediate rounded hillocks and 

 ridges, resembling the little pits and ridges that appear on the surface 

 of a piece of limestone that has been steeped in acid. Most of these 

 cavities were about three feet in diameter, and their depth varying 

 from one to two feet. Both the elevated and depressed portions of the 

 chalk had the same smooth and somewhat glossy surface that compact 

 limestone presents after corrosion by an acid. 



Dl". Buckland referred all these phaenomena to the action of acidu- 

 lated waters, and was of opinion that the frequent volcanic eruptions 

 during the tertiary period might have impregnated the sea in certain 

 regions with carbonic acid, which would account for the extensive cor- 

 rosion and destruction which the chalk underwent at that epoch, when 



