Narrative of the surveying voyages of his majesty's ships Adventure and Beagle (vol.2): between the years 1826 and 1836 : describing their examination of the southern shores of South America, and the Beagles's circumnavigation of the globe

108 CLIMATE — PUMICE. Sept. known to naturalists, Mr. Earle made careful drawings of them, and Mr. Darwin preserved many in spirits. We pro- cured plenty of good fresh water from wells near the beach, and small wood for fuel in their immediate neighbourhood. The climate is delightful, and healthy to the utmost degree, notwithstanding such extensive flats, half-covered with water, and so many large mud-banks. Perhaps the tides, which rise from eight to twelve feet, and run two or three knots an hour, tend to purify the air ; indeed, as the whole inlet is of salt water, there may be no cause for such effects as would be expected in similar situations near fresh water. In our rambles over the country, near Port Belgrano, we every where found small pieces of pumice-stone ; and till Mr. Darwin examined the Ventana, supposed they had been thrown thence : he has, however, ascertained that it is not volcanic and, I believe, concludes that these fragments came from the Cordillera of the Andes.— (See Vol. III. by Mr. Darwin.) Falkner, in whose accounts of what he himself saw I have full faith, has a curious passage illustrative of this supposition and it is not impossible — nor even, I think, improbable — that some of the pumice we saw fell at the time mentioned in the following extract : — " Being in the Vuulcan, below Cape St. Anthony, I was witness to a vast cloud of ashes being carried by the winds, and darkening the whole sky. It spread over great part of the jurisdiction of Buenos Ayres, passed the river of Plata, and scattered its contents on both sides of the river, insomuch that the grass was covered with ashes. This was caused by the eruption of a volcano near Mendoza, the winds carrying the light ashes to the incredible distance of three hundred leagues or more."" — Falkner, p. .51. As an indisputable, and very recent instance of the distance to wliich volcanic substances are sometimes carried, I might mention the fact of H.M.S, Conway having passed through quantities of pumice-stone and ashes, in latitude 7° north, and longitude 105° west, being more than seven hundred miles from the nearest land, and eleven hundi-ed from the volcano near Realejo, whence it is supposed that they proceeded ; but as it is