100 EARTH FEATURES AND THEIR MEANING 



conduits for the molten lava. This is well illustrated by the 

 cratered monticules raised by the common ant over the cracks 

 _ which separate the blocks of cement 



sidewalk, the hillocks being located 

 where the most favorable channel was 

 found for the elevation of the mate- 

 rials. 



Those places upon fissures which be- 

 FIG. 92. Diagrams to illustrate come lava conduits appear to be the 



the location of volcanic vents oneg where t h e cleft gapes widest SO as 

 upon fissure lines, a, openings . 



caused by lateral movement of to furnish the widest channel. Wher- 

 fissure walls ; b, openings formed ever a differential lateral movement of 



at fissure intersections. the walls hag occurred, openings Will 



be found in the neighborhood of each minor variation from a 

 straight line (Fig. 92a). Wherever there are two or more series 

 of fissures, and this would appear to be the normal condition, 

 places favorable for lava conduits occur at fissure intersections. 

 Within such veritable volcano gardens as are to be found in Ma- 

 laysia, the law of volcano distribution became apparent so soon as 



Fio. 93. Outline map of the eastern portion of the island of Java, displaying the ar- 

 rangement of volcanic vents in alignment upon fissures with the larger mountains 

 at fissure intersections (after Verbeek). 



accurate maps had been prepared. Thus the outline map of a por- 

 tion of the island of Java (Fig. 93) shows us that while the vol- 

 canoes of the island present at first sight a more or less irregular 

 band or zone, there are a number of fissures intersecting in a net- 

 work, and that the volcanoes are aligned upon the fissures with 

 the larger cones located at the intersections. So also in Iceland, 



