Washington — Catalan Volcanoes and their Rocks. 241 



for this rare constituent, while its presence in approximately 

 similar amounts in the other specimens was indicated by the 

 greenish color of the filtrate from the ammonia precipitate. In 

 this respect, as in the high titanium, these rocks resemble the 

 basalts of Sardinia, Pantelleria, and Linosa. 



Relations to other Districts. 



It would seem most natural to connect the igneous rocks of 

 the Catalonian volcanoes with those of the igneous areas which 

 extend in a well-defined zone clown the east coast of SjDain ; 

 including the Colnmbretes Islands,* the islands of Mallorca 

 and Iviza,f the igneous areas of Murcia:}; and Cabo de Gata,^ 

 and the island of Alboran.|| This connection is, indeed, 

 assumed to be true by the Spanish geologists, as Quiroga and 

 Calderon,*j[ who also point out the preponderance of salic rocks 

 toward the southern end and of more femic ones towards the 

 northern. While the tectonic relations and those of time, as 

 most of these eruptions are, apparently, of comparatively 

 recent geologic date, like the flows and cones of Catalonia, 

 favor this view, yet it cannot be accepted as definitely proven. 



With the exception of the Murcian rocks, of which excellent 

 analyses by Dittrich are published by Osann, the analyses of 

 the other localities leave much to be desired both as to com- 

 pleteness and accuracy. Titanium especially is apt to be neg- 

 lected in them, and the amount of this constituent is a highly 

 important feature of the more femic rocks, for the purpose of 

 comparison with those of Catalonia. In the only analyses in 

 which it is reported, those of the rocks of the Columbretes and 

 of Murcia, the amounts are low, the highest figure being 1*60 

 per cent, in a verite of Fortuna in Murcia, so that there is lit- 

 tle resemblance in this respect with the Catalan rocks. Fur- 

 thermore, the Murcian rocks described by Osann are relatively 

 and absolutely much higher in potash, and leucite even appears 

 in some of them, while hornblende and biotite are not uncom- 

 mon at many of the localities south of Catalonia. It would 

 seem best, therefore, to look upon any connection of the Cata- 

 lan rocks with those of the more southerly localities with 

 doubt, and as a matter to be settled in the future by more sat- 

 isfactory analyses and further investigation. 



The possibility may be suggested here of a connection of the 



Catalan rocks with those of the central volcanic line of Spain, 



*F. Becke, T. M. P. M., vol. xvi, p. 155, 1896. 

 fCf. S. Calderon, Bull. Soc. Geol. Fran., vol. xiii, p. 112, 1885. 

 % A. Osann, Rosenb. Festschr., p. 263, 1906. 



§ A. Osann, Z. d. G. G., vol. xl, p. 694, 1888 ; vol. xli, p. 297, 1889 ; vol. 

 xliii, pp. 323, 688, 1891. 



|| F. Becke, T. M. P. M., vol. xviii, p. 525, 1899. 



1 Cf. Calderon, Bol. Soc. Esp. Hist. Nat., p. 335, 1905. 



