Ch. XXIX] AQUEOUS EROSION IN PALMA. 507 



we could assume that the sea once entered the Caldera here as well 

 as by the great Barranco, it might have produced such a breach as <?, 

 and such an extension of the line of cliffs as that now observable 

 between e and a, map, p. 494, without any corresponding cliff to the 

 westward of e, a. 



Yet we could discover no elevated outliers of conglomerate to attest 

 the supposed erosion at the Cumbrecito, which is about 3500 feet above 

 the level of the sea. It might also be objected to the hypothesis of ma- 

 rine denudation in Palma, that there are no ranges of ancient sea-cliffs on 

 the external slopes of the island. The flanks of the mountain, except 

 where it is furrowed by ravines or broken by lateral cones, descend to the 

 sea with a uniform inclination. In reply to such a remark, I may ob- 

 serve that we do not require the submergence of the uppermost 3000 feet 

 of the old cone in order to allow the sea to enter both the great Bar- 

 ranco and the Cumbrecito and to flow into the Caldera. It would be 

 enough to suppose the land to sink down so as to permit the waves to 

 wash the base of the basaltic cliffs in the interior of the Caldera, and to 

 wear a passage through the Cumbrecito where there may have been 

 always a considerable depression in the outline of the upper formation. 

 But would not the same waves which had power to form in the Bar- 

 ranco a mass of conglomerate 800 feet thick have left memorials of their 

 beach-action on the external slope of the island ? No such monuments 

 are to be seen. It may be said, in explanation, — first, that cliffs are not 

 so easily cut on the side of an island towards which the beds dip as on 

 the side from which they dip ; secondly, if some small cliffs and sea- 

 beaches had existed, they may have been subsequently buried under 

 showers of ashes and currents of lava proceeding from lateral cones during 

 eruptions of the same date as those which were certainly contemporaneous 

 with the conglomerate of the great Barranco. 



On the eastern coast of Palma, about half a mile from the sea, in 

 the ravine of Las Nieves, not far from Santa Cruz, we observed a con- 

 glomerate of well-rounded pebbles having a thickness of 100 feet, 

 covered by successive beds of lava, also about 100 feet thick. In this 

 instance the ancient gravel beds occupy a position very analogous to the 

 buried cone, s.p., fig. 645, p. 496. "When in Palma, I conceived them 

 to be of fluviatile origin ; but, whether marine or freshwater, it must be 

 admitted that the superposition of so dense an accumulation of lavas 

 to a mass of conglomerate 100 feet thick shows how easily the outer 

 slopes of the island may have been denuded by the sea and yet dis- 

 play no superficial signs of marine denudation, every old beach or delta 

 once at the mouth of a torrent being concealed under newer volcanic out- 

 pourings. 



Since the cessation of volcanic action in the north of Palma, the most 

 frequent eruptions appear to have taken place in a line running north and 

 south, from a to Fuencaliente, map, p. 494 ; one of the volcanoes in this 

 range, called Verigojo, g, being no less than 6565 English feet high. 

 The lavas descending from several vents in this chain reach the sea both 



