Lieut. Nelson on the Geology of the Bermudas. 105 



but seldom exceeding a few square yards in surface^, and a few inches in 

 depth*. 



The islands are covered with about a foot of dry, red earth, containing 

 vegetable matter, and behaving before the blowpipe exactly like common 

 aluminous earth. 



The only minerals which have been noticed, are small pieces of oxide of 

 iron, of very questionable origin ; menaccanite, found near the ferry between 

 St. George's Island and Bermuda or Main Island ; arragonite, and a minute 

 quantity of manganese in the red earth. 



Unless immediately after a heavy shower, or when a fine cool morning acts 

 as a refrigerator to the evaporation of the preceding, sultry day, or in the im- 

 mediate neighbourhood of the marshes, the dew, though it does fall in all 

 places, is scarcely perceptible, owing to the porous nature of the rockf . 



Having thus briefly noticed the coincidences between the structure of the 

 Bermudas and the coral islands of the Pacific, I will mention an instance 

 which indicates a difference. Kotzebue says, 



" The reefs at Otdia consist principally of dark coral, which is mixed with but a little red ; at 

 low water the rocks are visible for about two feet, which was the case when we used the stream 

 anchor ; but all was soon covered by the rising tide. We had at a small distance from it forty 

 fathoms' depth, but which increased a little further so much that we could find no bottom^." 



This answers to the description of our serpuline reefs, but not of those 

 which owe their origin to zoophytes. The observation was made by Kotze- 

 bue, and seems to have been overlooked by Chamisso. It is proper to 

 add, although the animal of the Serpula can live for many hours out of the 

 water, yet that of most corals, on exposure, deliquesce in a few minutes into 

 a slimy liquid. 



The tides at Bermuda average about four feet six inches ; and at low water 

 the serpuline reefs stand about two feet above the surface. The variations 

 in the outside soundings, are by no means as rapid as in the South Sea coral 

 islands. 



* Capt. Kotzebue says, " The greatest depth in the whole group (Capeniur) was twenty 

 fathoms. In our anchorage place we had only six fathoms : the bottom consisted of white clay, a 

 circumstance which we had not met with in any other group." As this clay is noticed by Captain 

 Kotzebue^ and not by either of the naturalists, it is very probable that the word ' clay ' was used 

 without respect to its more specific meaning, as restricted to aluminous earth. The local name 

 for the Bermudian chalk, is pipe-clay. 



t Kotzebue says (vol. ii. p. 45.) " no dew falls," and (vol. i. p. 152. vol. 3. p. 145.) " the in- 

 habitants depend on rain for their supplies of fresh water ; of which, however, there is no want in 

 the larger islands, as it rises in pits dug for the purpose." 



X Vol. ii. p. 16. 

 VOL. V. — SECOND SERIES. P 



