324 Mr. S. V. Wood on some Tubular Cavities in 



though not all in the same state of compactness or density, the 

 acid would act alike upon the more indurated as upon the less 

 solid material, whereas a mechanical agent would be directed to 

 the place of least resistance ; and had the looser fragments 

 then been removed the nodules of compact corals would have 

 projected from the sides of the tubes. The whole aperture has 

 a lining or coating upon its walls such as might be expected as 

 the residuum adhering to the sides deposited by the evaporation 

 of the carbonic acid gas : this covering or lining of the sides of 

 the chimney is of an ochreous colour and of an aluminous com- 

 position, and may perhaps have been thicker than what now 

 remains, as exposure to the rain and weather would leave only a 

 small portion adhering to the crag. 



One cause to which Sir Charles Lyell alludes regarding the 

 possibility of his funnel-shaped tubes having been formed by the 

 large tap roots of trees that had decayed away, and the aperture 

 so left afterwards filled up by the falling in of the superincum- 

 bent gravel, could not be applicable as a cause for the pi'oduction 

 of these chimney pipes, which are much too regular in form to 

 have been so produced. 



In some jjarts of the coralline crag at Ramsholt I have met 

 with several caves or openings, such as might have been produced 

 by the subsidence or contraction of the clay beneath. One 

 of these was so small as to be not more than a foot or 18 

 inches in height, such as would scarcely admit a man to crawl 

 in, with a width only of a few feet : another somewhat larger, 

 near the same locality, has been in former times used by smug- 

 glers as a place of retreat. These fractures seem to have been 

 near the bottom of the crag, which at this place has a thickness 

 of not more than 6 or 8 feet ; the upper or more coralline poi'- 

 tion has been washed off and the red crag is superimposed, 

 while the London clay is visible immediately beneath, showing 

 portions of all three deposits above the level of the river Deben. 

 These cavities of a distant locality in the coralline crag are here 

 mentioned as indicating the probability that similar fractures 

 and openings exist in various other parts. 



There is every reason to believe that these gravel-filled cavities 

 were not eroded from above, either chemically or mechanically, 

 but that the openings under notice were formed by the evolution 

 and upward issue of acidulated gases. To produce this effect, it 

 is necessary to suppose these tubes to have been connected with 

 cavities or fissiu'cs in or through the clay beneath where the car- 

 bonic acid or other gases might have been elaborated. The 

 regular ajid tranquil deposits of these older tertiary clay beds, as 

 seen in England, give no indication whatever of any proximity 

 to volcanic action even in its most subdued form ; and the pro- 



