Narrative of the surveying voyages of his majesty's ships Adventure and Beagle (vol.3)

594 AZORES. Sept. 1836. then by a slight change in the set of ciirrents, the loose matter removed, so that the hard nucleus alone was left. Although the swell of the open ocean breaks heavily on the outside of this narrow and insignificant line of reef, yet there is no record of its decay. This durability is much the most curious circumstance in its history. Its protection appears due to a layer of calcareous matter, formed by the successive growth of several kinds of organic bodies, chiefly serpulee, balani, nulliporee, but no true corals. It is a process strictly analogous to the formation of peat ; and like that substance, its effects are to preserve from degradation the matter on which it rests. In true coral reefs, when the upper extremities of the living mass are killed by the rays of the sun, they become enveloped and protected by a nearly similar process. It is probable, that if a breakwater, such as that at Plymouth, was built in these tropical seas, it would be imperishable ; that is, as imperishable as any part of the solid land, all of which must some day suffer decay and renovation. On the 17th we took our final leave of the coast of South America, and on the last day of the month anchored at Porto Praya. We staid there only five days, and on the 5 th of Septeinber steered for the Azores. On the 19th we anchored off the town of Angra, the capital of Terceira. This island is moderately lofty, and has a rounded outline, with detached conical hills evidently of volcanic origin. The land is well cultivated, and is divided into a multitude of rectangular fields by stone walls, extending from the water's edge to high up on the central hiUs. There are few or no trees, and the yellow stubble land at this time of the year gave a burnt-up and unpleasant character to the scenery. Small hamlets and single whitewashed houses are scattered in all parts. In the evening a party went on shore : we found the city a very clean and tidy little place, containing about 10,000 inhabitants, which includes nearly the fourth part of the total number on the island. There are no good shops, and there is little appearance of actiAatv, excepting