598 



described above, have been laid down graphically — first and 

 foremost as the embodiment of their working hypotheses, whicli in 

 some details are reliable, but whose general trustworthiness must be 

 called in question. 



The maps and profiles cannot be unreservedly accepted. Only 

 more prolonged and more minute investigations than V. and F. were 

 able to perform, will have to demonstrate for every part of the 

 island whether the writers are right in their generalising assertions 

 about the geology of Java, or svhether their mapping has to undergo 

 a thorough revision. 



On the geological map of Java old andesites, brecciated and marly 

 miocene and recent eruptive rocks have been indicated to the east 

 of Buitenzorg ^). A number of excursions made in this district enable 

 me to form an estimate of this uiappiug. 



Up to about 45 km. before the Poentjakpass the great highroad 

 from Tjiandjoer to Buitenzorg, runs over the young, volcanic mantle 

 of the Gedeh-Pangrango-massif. According to the geological map it 

 then crosses a mountain giound of old andesites and basalts, which 

 in the South leans against the Northern declivities of the Pangrango, 

 and extends towards the North, broadening rapidly, as far as nearly 

 15 km. north of the Poentjakpass. The southern part of these old 

 eruptive rocks (G. Gedogan, Djoglok, Soemboel and Gegerbentang) 

 is, according to the geological map, as it were, pinched off from 

 the more northern tracts by the young volcanic massif of the G. 

 Limo. In the landscape these "old andesites" do not seem to be 

 distinguishable from the "young volcanoes". Nor do the large num- 

 ber of andesite blocks on the Batavia-side of the Poentjak, visible 

 from the tea-gardens, look less fresh than those found on the slopes 

 of the Gedeh. It appears, then, that after traversing the district once 

 no evidence whatever can be adduced, to show the existence of two 

 volcanic massifs of entirely different age. 



The other arguments brought forward by Verbeek and Fennema 

 in their "Geology of Java and Madoera" to support their hypothesis 

 that in this region the old miocene eruptive rocks are detached 

 from the young volcanoes, are not quite satisfactory. In the French 

 edition (p. 506) we read: "Aiitant qu'on ait pu juger par les afleure- 

 ments insuffisants, les sediments tertiaires semblent reposer au Nord 

 et a rOuest sur l'andésite et conti-e celle-ci". It seems, therefore, 

 that, as regards the normal superposition of the tertiary sediments 

 on the old andesites — which would indeed prove the age of the 



M Sheets All, Alil. BlI, Bill. 



