2^1 



The composition of a calc-silicate-hornfels fi-om tlie Wai Najo is, 

 according to the analysis of Prof. Dr. M. Dittrich of Heidelberg, 

 as follows: 



SiO' 59,60 



TiO^ 0,46 



Al'O' 7,90 



Fe'O' 0,64 



Cr"-0' trace 



FeO 6,02 



MnO 0,28 



CaO 15,20 



MgO 5,35 



K'O 0,57 



N'a^O 1,98 



P'O' 0,22 



CO' 0,69 



H'O (under 110°) 0,17 



HU) (over 110° to 1250°) . . . 1,32 



100,40 



The specific weight is 3.213. From the analysis it appears that 

 the result of the chemical composition in consequence of the contact- 

 metamorphosis of the Jurassic marls is the disappearance of C0^ 

 which, as in other similar rocks, is found only in a very slight 

 quantity'. The water was likewise for the greater part evacuated. 

 A modification of the composition with regard to the other con- 

 stituents cannot be observed. The resiills of the analyses ofthecalc- 

 silicate rocks vary greatly, which is not astonishing on account of 

 the great variety of the sediments that gave occasion to their 

 formation. 



The fact that the youngest strata of the Jurassic system in Taliabu 

 were interspersed with granite and metamorphosed, is of great im- 

 portance; its eruption can consequently not have taken place earlier 

 than during the Cretaceous system. 



The occurrence of granite of mesozoic age was hitherto only 

 stated or made probable in the Malay peninsula by J. B. 

 ScRiVENOR^), in Sumatra by Aug. Tobler^) and R. D. M. Verbeek''), 



V The Rocks of Pulau Ubin and Pulau Nanas (Singapore). Quart. Journ. Geolog. 

 Soc. 66. London 1910. p. 4i29. — The Geologic History of the Malay Peninsula. 

 Quart Jüurn. Geolog. Soc. 69, London 1913, p. 351. 



-) Voorloopige mededoeling over dc gpologie van de residentie Djambi. Jaarboek 

 van het Mijnwezen in Ned. Indie 39. lülü. Batavia 1912, p. 18-19. 



S) Koloniaai-Aardrijkskundige Tentoonstelling. Amsterdam 1913. Catalogus, p. 76, 



16* 



