23 



The closer to the crater the finer materials came down, the lower 

 was their temperature ') 



Together with the ashes were ejected innumerable large blocks -) 

 of pumice, containing very hot gases. As with increase of the size 

 of objects, the surface and hence also the resistance of the air and 

 the eradiation of heat increase in ratio much less than the weight, 

 these blocks remained a much shorter time in the cold air-zones 

 and lost by a double cause much less heat: they were probably 

 somewhat cooled on the outside, but must have been still very hot 

 within when come down *). Such large heavy blocks which from a 

 height of thirty or perhaps fifty km. fell down at an enormous speed 

 could not come to a standstill on the higher, steeper slopes /f ) of 

 the cone, but, as is generally observed ') during volcanic eruptions, 

 leapt and rolled down until they reached the lower less steep parts 

 where they came to rest. Consequently these lower parts have been 

 much more deeply buried than the higher ones. One can distinguish 

 on the south and south-eastern sides of Krakatao two zones, of 

 course not clearly demarcated: the higher parts above 400 600 m. 

 which were covered only with a rather thin and not very hot layer 

 of ashes and grit 1 '), and the lower, more gently sloping parts covered 



M Of course I do not mean such very fine eruptive products as were shot up to 

 a very great height, were there cooled very much, and carried away by strong winds, 

 fell down far from Krakatao. 



-) Verbeek | Krakatau, Dutch Edition (1888), p. 12'2| s llw on Krakatao blocks 

 of 1 cubic metre in sire. De lough (|aarboek van het Mijnwezen in Nederlandsch 

 Oost-lndie 100N No- 'i2) roughly estimates that the eruptive products consisted for 

 15 25% of pieces of pumice varying in size between that of a pea and of a human 

 head, for 3 5% of blocks of hard rock, for the rest of volcanic ashes. 



3 ) The initial temperature of the ejected materials must have been more than 

 800 C. It seems [Cf. Kern mer ling, Vulkanol. Meded. II (1021), p. 78] that volcanic 

 gases are enclosed in the pumice and can escape only very slowly. 



') See plate II made after plate XXVII in [aarverslag lopogr- Dienst Ned. Indie, 

 1008, and cf. Ernst. Neue Flora Vulkaninsel Krakatau (1007) tab. Ill, fig. 4. Cf. also 

 Ernst, I. c- p- 28; ,,Nach Siidosten senkt sich der halbierte Kegelberg steil gegen 

 einen flacheren Fuss. "-De longh (]aorboek van het Mijnwezen in Nederlandsch 

 Oost-lndie' 1010, p. 45) expresses the opinion that during the eruption the ashes fallen 

 on the higher part of the cone, slided off. 



|V ) Cf. i. a. the description by |unghuhn, |ava, 2nd Dutch Edition III, 783, 1120; 

 German Edition II, ;)4iJ, 760) of the eruptions of Mount Smeroe and Mount Lamongan. 

 Also Kemmerling, Vulkanol. Meded- No. 3, p. 4 



") I he statement of Docters van Leeuwen [Ann. |ard. Bot. Buitenzorg XXXII 

 (102:!) 1 :?'.)( and Dammerman (Treubia II, 73) that the ashes fallen on Krakatao 

 must have been much hotter than these fallen on Sebesi about 20 km. to the north, 

 is consequently incompatible with well-stated facts- The great heat on Krakatau was 

 not caused by ashes but by hot blocks of pumice. On Sebesi no very big blocks 

 of pumice-stone have fallen. Accoiding to Verbeek | Krakatao, Dutch Edition 

 (1888), p. 122 1 on the latter island pieces as big as a human head are already scarce. 

 ..Generally speaking the large and heavy blocks of pumice fell within a circle of 

 15 km. radius around Krakatau. 1 he materials fallen outside this circle consist for 

 the greater part of ashes". I herefore the vegetation of Sebesi suffered much less 

 than that of most parts of Krakatao. 



