ON ITS EXTERIOR. VOLCANOES. 285 



ness, that, with the view of inciting others to new 

 investigations, I think it desirable to call attention to 

 this feature. Junghuhn says, " Although the face of a 

 conical volcano 11,000 feet high, Grunung Sumbing, 

 seen from some distance appears like an uninterruptedly 

 smooth incline, yet on a nearer view it is # found to 

 consist of separate long narrow ridges or ribs, which 

 become more and more divided, and wider, in descending. 

 They proceed from the summit, and still more 

 frequently from a height of a few hundred feet below 

 the summit, to the foot of the mountain, diverging on 

 all sides like the ribs of an umbrella." These long 

 ridges or ribs have sometimes for a short distance a 

 winding course; they are all divided from each other 

 by intervening clefts 300 or 400 feet deep, which also 

 widen out in descending. These radiated furrowings 

 of the surface are found "on the sides of all the 

 volcanoes in Java, but with considerable differences in 

 regard to their mean depth and to the distance of their 

 upper commencement from the margins of the craters 

 or the unopened summits of the different mountains. 

 Grunung Sumbing, 11,030 feet high, is one of those 

 which show the finest and most regularly formed ribs, 

 and with the greatest distinctness, as the mountain is 

 without forest trees and is covered with grass." Accord- 

 ing to the measurements given by Junghuhn ( 417 ), the 

 subdivision of the ribs increases with the decreasing 

 angle of inclination. Thus, in GK Sumbing, above the 

 zone of 9000 French feet there are only about 10 such 

 ribs; at 8500 Fr. feet there are 32 ; at 5500 Fr. feet, 

 72 ; and at 3000 Fr. feet (3197 English), above 95 ;- 

 the angle of inclination decreasing at the same time 



