47 



e.g. a patch of rank herbage beside the railway station at Blitar. 

 (See this pag.) 



In our flow, on the other hand, the average thickness is fifty 



Photo from Helmig & Company. 



Volcanic debris from the Lahar of Klut at Blitar about 

 5 km. above the termimus of the flow. The unburned 

 buildings and unwithered herbage show that the lahar 

 could not have been very hot at this point. 



times as great, indicating an entirely different sort of fluid. It is 

 doubtful indeed if the minimum thickness of our flow was as low 

 as the average thickness at Klut. Few, if any of the deposits lift on 

 the ground are less than a meter thick Clear out to the very tip 

 it retained an excessively high temperature. For a considerable 

 distance beyond the present end of the flow material one finds 

 stumps of bushes burned off by the iieated material that once covered 

 them but has been eroded away. Outside the limits of the flow 

 itself moreover all trees were killed for some distance and grass 

 fires were started well down toward the tip. See pages 48 and 49. 



The deposits left behind, while different from the lahar of Klut, 

 resemble closely those of the "incandescent avalanches" of Pelée 

 and La Soufrière as described by a number of observers, e.g. 

 Anderson and Flett ^). 



This similarity together with the increasing evidence of a high 

 temperature brought out by further study has convinced us as 

 detailed by Fenner ') that the tuff filling the Valley of Ten Thousend 

 Smokes originated as an outpour of red-hot material very much like 

 the incandescent avalanches that rolled down the slopes of Pelée 

 and La Soufrière in 1902. 



The differences between these and the hot sand flow with which 

 we are dealing appear in fact to be due to differences in the cir- 



1) Phil. Trans. Royal Society, A vol. 200 ; p. 492 et seq. 506 et seq. 

 ») 0. p. cit. p. 577. 



