114 GEOLOGY. 



base of Mount Loa. It is a chasm eight miles in circum- 

 ference, and situated in the midst of another chasm still 

 greater in extent, that is surrounded by a precipice vary- 

 ing from 200 to 400 feet in height. In the midst of the 

 inner chasm stand up fifty or sixty conical craters, many 

 of which are continually in action. Rivers of melted lava 

 run about among the craters, and red-hot stones, with cin- 

 ders and ashes, are sent up with flame from those which 

 are active, in some cases to an immense height. 



198. Tomboro, This is a volcanic mountain in the isl- 

 and ofSumbawa. Lyell thus speaks of an eruption of it 

 in 1815: "It began on the 5th of April, and was most 

 violent on the llth and 12th, and did not entirely cease 

 till July. The sound of the explosions was heard in Su- 

 matra, at the distance of 970 geographical miles in a di- 

 rect line, and at Ternate, in an opposite direction, at the 

 distance of 720 miles. Out of a population of 12,000, only 

 twenty-six individuals survived on the island. Violent 

 whirlwinds carried up men, horses, cattle, and whatever 

 else came within their influence, into the air; tore up the 

 largest trees by their roots, and covered the whole sea 

 with floating timber. Great tracts of land were covered 

 with lava, several streams of which, issuing from the cra- 

 ter of the Tomboro Mountains, reached the sea. So heavy 

 was the fall of ashes that they broke into the president's 

 house at Birna, forty miles east of the volcano, and ren- 

 dered it, as well as many other dwellings in town, unin- 

 habitable. On the side of Java the ashes were carried to 

 a distance of 300 miles, and 217 toward Celebes, in suffi- 

 cient quantity to darken the air. The floating cinders to 

 the windward of Sumatra formed, on the 12th of April, a 

 mass two feet thick and several miles in extent, through 

 which ships with difficulty forced their way. The dark- 

 ness occasioned in the daytime by the ashes in Java was 

 so profound that nothing equal to it was ever witnessed 

 in the darkest night." 



199. Graham's Island. This island rose up out of the 



