364 REACTION OF THE INTERIOR OF THE EARTH 



Ratuh mountains, is very near, and has formations of 

 serpentine, gabbro, and syenite. ( 494 ) 



In the other three great Sunda Isles, Sumatra, Java, 

 and Celebes, Junghuhn counts of active volcanoes; in 

 Sumatra 6 or 7, in Java 20 or 23, and in Celebes 11; 

 to Flores he assigns 6. We have already spoken in 

 detail, p. 280 to 288, of the volcanoes of Java. In 

 Sumatra, which has not yet been thoroughly explored, 

 out of nineteen conical mountains which have a vol- 

 canic appearance, six are active volcanoes. ( 495 ) Those 

 recognised as such are : Gunung Indrapura, about 11,500 

 French feet (12,256 English) according to angles of 

 altitude taken at sea (perhaps its height is similar to 

 that of the more exactly measured G. Semeru or Maha- 

 Meru in Java); Grunung Pasaman, also called Ophir, 

 which was ascended by Dr. L. Horner (9602 feet), with 

 an almost extinct crater.; Grunung Salasi rich in sulphur; 

 it erupted scoriae in 1833 and 1845 ; Gunung Merapi, 

 (9570 feet) also ascended by Dr. L. Horner in company 

 with Dr. Korthal in 1834, the most active of all the 

 volcanoes of Sumatra, and not to be confounded with 

 the two mountains of the same name in Java ( 496 ) ; 

 Gunung Ipu, a truncated cone which sends forth smoke; 

 and Gunung Dempo, in the inland district of Bencoolen; 

 its height is estimated at 10,000 French feet (about 

 10,660 English). 



Four small islands, cones of trachyte, of which Peak 

 Rekata and Panahitam (the Prince's islands) are the 

 highest, rise in the Strait of Sunda and connect the 

 Sumatra range of volcanoes with that of Java ; and in a 

 similar manner, at the eastern end of Java, its eastern- 

 most volcano, Idgien, is connected by the active volcanoes 



