186 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Feb. 20, 



half that from the latter, with a depth of water varying from half 

 a fathom to a fathom. This island, which rises to a height of about 

 thirty feet, is formed of calcareous stone, having a western dip of 

 about 30° and covered in many parts by coarse sandstone. This is 

 very uneven and is traversed in various directions by veins of much 

 harder texture, which rise above the surrounding surface, forming 

 sharp ridges intersecting each other at various angles. 



This island is nearly circular, and the outer part of its circumfer- 

 ence is hollowed by the action of the waves and currents, leaving a 

 projecting ledge, forming a kind of penthouse, varying in width from 

 six to fifteen feet, and generally thinnest on its outer part, On 

 many spots this has broken off, and the fragments have fallen on 

 the shore, where they remain. These fractures have mostly been 

 caused by cylindrical holes which perforate the thickness of the 

 ledge. The substance which caused these holes sometimes remains 

 adherent either in the persistent or the detached portion ; and in 

 other spots the ledge remains entire, with the foreign body project- 

 ing both above and below its surfaces. In the latter position, it is 

 generally tapering at the lower end ; and a portion of the same sub? 

 stance, of corresponding size, may be perceived at the bottom of the 

 sea : this portion is sometimes worn to a level with the surrounding 

 surface by the action of the waves. 



The landward side of the island is destitute of the projecting 

 ledge which marks the seaward border, and is rent into deep fissures 

 in various spots. Adhering to the sides of these may be perceived 

 considerable masses of the same material as that found in the 

 holes mentioned, which seem to have formed portions of trees, of much 

 larger dimensions than those which are found in the holes mentioned. 



The surface of the island is very unequal ; and in many parts cy- 

 lindrical holes are perceived which extend to the sea-level. The re- 

 gularity of their form is very remarkable. Their diameter varies 

 from 1 to 2 feet. 



On the surface, in the sandstone which covers the calcareous rock, 

 are many fissures radiating from a hollow which appears to have 

 been caused by the base of a tree, as the fissures have been by its 

 roots. On other spots, numerous stumps are seen, §ome of which are 

 as much as three feet long, corresponding in diameter with those 

 found on the ledge ; and a much greater number of smaller size and 

 height are scattered among them. The former have the appearance 

 of exogenous trees ; and their form and colour, when viewed from a 

 distance of from twenty to thirty yards, might easily cause them to be 

 mistaken for wood. The outer part is in most cases of the ashy grey 

 seen on old dead bark. The interior is more or less hollowed, leav- 

 ing an uneven border ; and the inside is exactly of the colour of 

 rotten wood, and is in every case perforated with numerous holes, 

 bearing a resemblance to those produced by white ants, but of larger 

 calibre. The same colour and riddled appearance is often seen on 

 the outside of the stump, and always on the inside. The smaller 

 stumps appear to have belonged to endogens of the Palm tribe ; and in 

 many individuals the medullary substance has entirely disappeared, 



