168 



Sketch of the Geology of the 



[Jan. 



of the island, the surface is completely covered with a coating of salt, 

 left by the evaporation of the sea-water, which periodically inundates 

 the low ground. This salt in its impure Mate is employed as a condi- 

 ment by most of the natives and naturalized inhabitants of the neigh- 

 bourhood. Without drawing any very general or sweeping conclusions, 

 from the fact of the existence of a receut salt deposit in this situation, 

 we cannot fail to remark, that an extensive formation is actually in the 

 course of being produced, for the product of the disintegrated rocks, 

 will obviously be spread successively over each saline residuum, and as 

 each new bed is laid, the subtrata will acquire additional firmness and 

 solidit)^, combined with the agency of the high mean temperature, which 

 the most trivial observer will detect as a powerful agent in tropical coun- 

 tries, in binding together the most arid particles.* 



This valley is formed by a break in the continuity of the basaltic 

 ridge, the southern portion of which terminates here, but resumes its 

 altitude and course near Tanna. The vale is overlooked by the hill 

 which forms the extremity of the ridge. The ruin of a Portuguese 

 chapel crowns its summit, consisting of the basalt, (a gray rock with 

 augite crystals interspersed, which forms its foundation, No. 1,). At 

 the base of the ridge near the shore is a similar ruin, built of porphyry, 

 and at each of them there is a corresponding inscription on sand-stone 

 tablets, which must evidently have been procured from a great distance. 



The words of the inscription are contracted, and are in the Portuguese 

 language. They relate to some individual of Che name of Aquias, pro- 

 bably a priest, as the word sevsesdros occurs ; and the dates of the 2d of 

 April 1620, and 28th November 1630 appear. 



Near it is situated a Mahometan garden, neatly laid out in the English 

 style, with grass walks, flower and vegetable borders, and a variety of 

 fruit trees. 



The ascent to the summit of the hill is rendered difficult, by the 

 abruptness of the declivity and the loose fragments containing mesolite, 

 chalcedony and quartz nodules, which readily yield to pressure, and 

 roll to the base of the hill. The degradation of rocks cannot better be 

 observed than in this neighbourhood, where we see them comminuting, 

 rolling to the base and assisting in elevating the level of the valleys, 

 and diminishing the relative height of the hills, of which a similarly 

 striking illustration is afforded at the north-west side of the Pyrenees.f 

 The product of this disintegration is well expressed by the German 

 epithet, geschiebe, the ratchill of the miners, and must necessarily con- 

 stitute the most recent formation wherever it occurs. 



* Some distinguished geologists have attributed-the colour of the red sand-stone to the 

 ferruginous parts of the porphyry, from whose disintegration, they consider this forma- 

 tion to be derived. Humboldt Essai geognostique sur le Gisement des roches, 2nd Edit, 

 Paris, 1826, p. 203. 



t Link's Travels in Portugal, 8yo, 1801, p. 64. 



