OF THE DEPENDENT ISLES OF TAIWAN. 31 



while the substance of the ilmeuite entirely disappears when 

 traversing other crystals, and comes again into view in the same 

 direction as a continuation of the interrupted crystals. Unfortu- 

 nately basal sections were not frequently observed, and this 

 was the greal obstacle in ascertaining the presence of ilmenite 

 11 microscopic analysis. The ore with above-mentioned lamellar 

 habit occurs exclusively in a coarse-crystalline type of intersertal, 

 or ophitic structure, irrespective of hyperstheue or olivine-bearing 

 Basalt ; and this fact lends evidently a strong support to the view 

 advanced by K. Hofmann,^^ that the ilmenite accumulates in the 

 lower portion of lava-flows, and in that which has crystallised 

 under high pressure, while the magnetite is rich in the upper 

 part that has consolidated under a low pressure. Fr. Sandberger-^ 

 says also that Basalts may be classified into Dolerite and Basalt 

 proper, by the presence of ilmenite in the former and magnetite 

 in the latter. These fruitful ideas inaugurated by both authors, 

 now unfortunately passing into oblivion, deserve the careful 

 attention of petrologists. 



A slide of the Basalt from the islet of Hatto was treated for 

 a considerable length of time with a strong hydrochloric acid 

 without any appreciable result. A large quantity of the jduI- 

 verised sample of the same specimen was then digested in 

 boiling HCl with the addition of tin-foil, and the solution was 

 coloured slightly violet, showing the presence of titanium in the 

 dissolved j)ortion of the ore. Ilmenite also occurs, according 

 to VénukoÔ"^ very abundantly in the Basalts of Mongolia, and 

 even transparent lamellae were found by him, just as in the Pes- 

 cadores rocks. The ilmenite is fresh and leucoxene not noticed. 



1) 'Basalt von Eakony,' Zeitschr. d. d. gcol. Ges., XXIX., 1877, S. 191. 



2) Eosenbusch, 'Mikroskopische Physiographie,,' II., 3te Auflage, S. 1015. 



3) ' Les Bodies Basaltiques de la Mongolie,' Bdl. Soc. belge de Géologie, etc. T. IL, p. 443. 



