luj I LIBRA! 



REPORT ON THE PETROLOGY OF OCEANIC ISLANDS. 



163 



These general remarks on the geological nature of this archipelago will suffice as 

 an introduction to the description of the volcano of Camiguin. 



This small island is situated between Siquijor and Mindanao, to the north of the 

 latter island, and 80 miles east of Zebu. The volcano of Camiguin, which stands hard 

 by the village of Catarman, was still in an active state when the Challenger Expedition 

 explored it in 1875. It was then re-entering upon a period of repose, after the terrible 

 eruption of 1871. According to the account of that catastrophe, which we borrow from 

 Professor Eoth, 1 the islands of Bagol, Zebu, and Camiguin had for some months been 

 suffering severely from earthquakes, until, on the 1st of May 1871, about five o'clock, 

 a mountain near Catarman was rent open ; a central cavity appeared, from which 

 ashes and stones were projected amid explosions and clouds of smoke. An elliptical 

 crater was formed, which measured 1500 feet along the major axis, 150 along the 

 minor, and attained a depth of 27 feet. At seven o'clock a second eruption occurred ; 

 but, like the first, it sent out no lava streams. After this catastrophe almost all the 

 inhabitants, to the number of 11,000, deserted the island. According to the details 

 furnished by J. G. Gray of the Eoyal Navy, 2 eruptions took place only in July, and 

 the phenomena of internal activity continued for nearly two months. The hill 

 was entirely formed during this eruption, and according to Mr. Gray it was about 

 two-thirds of a mile in diameter, and 450 feet high. When, in 1875, the naturalists 

 of the Challenger touched at Camiguin with the intention of studying this volcano, its 

 summit rose to a height of 1950 feet. The volcano is situated close to the shore. 

 Its form is that of a dome, resembling, according to Mr. Buchanan, some of the small 

 volcanoes in the Auvergne. When it was explored all traces of a crater had dis- 

 appeared, neither pumice nor scoriae were found ; the rocks were still incandescent at a 

 dull red heat, and, by night, the mountain was seen crowned with glimmering light. Hot 

 springs gushed from all the crevices at the foot of the volcano, 3 and fumaroles were to 

 be seen everywhere. The vapours which escaped from these had effected profound 

 changes in the neighbouring rocks. According to the observations of Buchanan and 

 Moseley, who collected the specimens we are about to describe, the volcano is situated 



1 Roth, he. cit., p. 335. This note on the eruption of the volcano of Camiguin appeared in the Spenersche Zeilung, 

 No. 167, 1871. 



2 Hydrographic Notices, No. 8, London, 1872. 



3 It is not within the scope of this description to report the very interesting observations which were made at the 

 volcano of Camiguin on the temperature conditions under which certain low plants live. For this point we refer the 

 reader to Narr. Chall. Exp., vol. i. p. G54 ; but the interest which, from a geological point of view, arises from these 

 questions induces us here to recapitulate the results. At places where the temperature of the hot springs reaches 

 65° C. , the presence of algae was not observed, but on some blocks that were bathed by the hot water, and rose above 

 the level of the current, greenish spots were noticed. A little below the source algae were found abundantly in a small 

 pool into which the water fell, and still retained a temperature as high as 38° C. Still lower they were seen growing in 

 the middle of a brook, whose waters reached 45°3 C, the highest temperature at which these plants were observed 

 to exist at Camiguin. The resistance which these organisms offer to high temperature is the more interesting, since 

 thermal waters are almost saturated with the various salts that result from the decomposition of the rocks they 

 traverse. 



