THE GALAPAGOS AECHIPELAGO. 269 



Climate. 



Althougli traversed by the equator, the Galapagos lie entirely within the 

 climatic zone of the southern hemisphere, for the south-east wind prevails regu- 

 larly, bearing its rains and its vapours to the upper slopes of the volcanoes. The 

 archipelago is also exposed to the influence of the southern marine currents. 

 After passing Cape Blanca, Humboldt's stream would seem to ramify into two 

 branches, one of which continues its northerly course, while the other sets north- 

 west and west in the direction of the Galapagos. In these latitudes both currents 

 have a normal temperature of about 73° Fahr , or 5° less than in the inter- 

 mediate space. In the archipelago this temperature is further diminished by 

 another current coming directly from the south ; west of Albemarle and Nar- 

 borough, Wolf recorded only 70° Fahr., while Fitzroy found places in the 

 neighbouring seas as low as 60° Fuhr. 



In the straits between the islands the currents move in some places north- 

 westwards with a velocity of over two miles an hour. Thanks to the coolness of 

 these currents, the archipelago enjoys a far more temperate climate than the 

 section of the continental seaboard under the same latitude. The mean tempera- 

 ture scarcely exceeds 70° Fahr. at sea-level, although in some of the islands 

 sheltered from the trade winds it may at times rise to 8G°, and even 95° during 

 the heat of the day. Speaking generally, the Galapagos may be said to have the 

 same climate as they would have if removed some 1,200 miles from the equator. 



The efftcts of this climate may be distinctly read on the mountain slopes. 

 Geologists may doubtless recognise the different ages of the erupted rocks. But 

 the chief contrasts are due, not to the nature or to the age of the igneous 

 formations, but to altitude and the vertical disposition of the climates. Up to a 

 height of 650 feet the bare rocks unexposed to any rainfall preserve their 

 primitive aspect. They have their crests, their protuberances, their cavities caused 

 by the explosion of gases, just as when they were first upheaved from the marine 

 depths. But on the higher slopes and summits the rocky surfaces have been 

 modified in accordance with the greater or less abundance of the rain waters 

 brought by the trade winds. These rains have dissolved some of the chemical 

 substances contained in the rocks, and disintegrated the rest, transforming the 

 surface of the rugged lavas to a layer of red clay. The jagged heights and 

 crests have been rounded off, and the whole covered with a dense vegetation. 



On all the upper slopes, where the rocks are seen from a distance cropping 

 out amid the surrounding verdure, the erupted matter is of too recent origin to 

 be yet clothed with forest growths. At an average height of from 650 to 

 about 800 feet the vegetation begins to girdle the mountain slopes, which are 

 black or red at their base, and on their summits clad with a mantle of green. 

 The cactuses and lichens, with here and there a few scrubby bushes, appearing in 

 the fissures of the lower rocks, are replaced higher up by a narrow belt of thinly 

 scattered trees, their branches draped with the " Spanish beard " and other para- 

 sitic growths. Then follow almost abruptly the dense leafy woodlands, the vege- 

 tation thus everywhere increasing in exuberance with the abundance of moisture. 



