608 



the "Old Andesites" originated only after tiie deposit of the Tertiary 

 clay-formation. 



CONCLUSION. 



The old andesites east of Buitenzorg are younger than the en- 

 circling sedimentary Tertiary. The bulk of the sedimentary Tertiary 

 east of Buitenzorg is developed as a clay-formation : only in the 

 recent levels breccia and allied rocks occur. Now it is still a moot 

 point whether the "Old Andesites" are the places of eruption, from 

 which the conglomerates and the breccia of the young Tertiary, in- 

 cluded in the folding, were extruded, and consequently are a little 

 older than Gedeh-Salak, or whether they are contemporaneous with 

 these volcanoes. That they are less high and that their volcanic 

 shape is less perfect, would seem to favour the first view. This 

 question, however, can be positively solved oidy through minute 

 researches in this volcanic region, so difficult to traverse, and through 

 petrographic investigations in connection with them. 



In the above we have pointed out, for one district, that the 

 geological map of Java, requires a thorough revisal. It would 

 not be ditficult, even by dint of comparatively little tieldwork, 

 to enlarge the number of instances. We do not mean to censure 

 the makers of the "Geological map". Those who hold that respect 

 is due to the men who performed a comprehensive task with only 

 little assistance, may still feel called upon to point to the short- 

 comings resulting from a superficial examination. The only fault of 

 the authors is, that in publishing an illusive map, indicating in 

 every place "continued" formation outlines, and accompanied by a 

 great many profiles, they have made us believe that we really 

 possess a rather detailed geological survey of this island. This is 

 why after the investigations by V. and F. the, necessity of further 

 geological work in Java has been given hardly a moment's 

 consideration. 



May this paper tend to produce the conviction that a minute 

 revision of the geological survey of Java, is of prime importance for 

 geological science. In practice a similar wish has frequently been 

 expressed, but in vain. 



Buitenzorg, 1 Jan. 1917. 



