Vol. I] WILLIAMS— BUTTERFLIES AND HAWK-MOTHS 291 



irregular shape, while the four next in importance — Chatham, 

 Indefatigable, James, and Narborough Islands, are each about 

 twenty-five or thirty miles long, and of a rounded or elongate 

 form — these are situated in a comparatively calm sea, where 

 storms are of rare occurrence, and even strong winds almost 

 unknown. They are traversed by ocean currents which are 

 strong and constant, flowing towards the northwest from the 

 coast of Peru." This, a portion of the great antarctic drift, 

 has the effect of making the climate of these islands, tropically 

 situated, quite temperate. Seldom indeed, then, is the heat 

 excessive, and it appears never to become really cold during any 

 period of the year. The northern extremity of the group is 

 influenced somewhat by the Panama current, so that it is 

 noticeably warmer there than farther south, though the natural 

 history does not appear to be modified in any manner thereby. 

 Lava of various ages occurs on all the islands, and forms 

 at least their exterior surface in a large measure. Narborough, 

 for instance, is covered almost entirely, from its huge crater 

 over 4000 feet high to the very sea-level, with a layer of recent 

 lava. Only here and there along its sides and base and perhaps 

 summit exist strips or patches of older layers, supporting a 

 meager flora and fauna. All the larger islands, especially 

 Albemarle, have great fields of lava. Charles and Chatham, 

 two of the more southern islands, could be, and are sometimes 

 considered (as regards external appearance) as the oldest 

 islands of the group. They have plenty of good rich soil and 

 their various craters are well rounded and sometimes almost 

 obliterated. The upper areas of the higher islands, especially 

 on their weather side (S. E. in this case) where the moisture 

 first strikes them, have an abundance of humus and vegetation. 

 With a few exceptions, the lowlands are quite arid and of 

 desert character. 



For some hundreds of years, the Galapagos Islands have 

 been visited by various ships and were formerly a favorite 

 resort of the buccaneers who were numerous in the region. 



In 1835, the Galapagos were visited by Charles Darwin in 

 the "Beagle" ; in 1852, by Prof. N. J. Andersson, in the Swed- 

 ish frigate "Eugenie"; in 1868-9, by Dr. A. Habel; in 1871, 

 by Prof. A. Agassiz of the "Hassler Expedition"; in 1875, by 



