34 HENRY S. WASHINGTON 



paper/ based on numerous analyses which had been made of material 

 collected during the trip on which Linosa was visited, especially of 

 the basalts, the same idea was again expressed, the rocks of Catalonia 

 being also considered as related to those of the other localities, and the 

 probable existence of a distinct comagmatic region (petrographic 

 province) in the western Mediterranean being pointed out. While 

 this conclusion is based partly on the character of the basalts, there is 

 considerable other evidence in its favor in the characters of the more 

 sahc rocks, and in other facts, but a full discussion must await the 

 publication of the whole series of analyses, many of which remain 

 to be made. In the present place it must suffice to point out the simi- 

 larities between the basalts along this zone. 



Turning to the table of analyses on page 32, it will be seen that 

 the chemical characters of the basalts of Pantelleria, Sardinia, and 

 Catalonia (only a few of which have been given here) are remarkably 

 similar to those of Linosa and of each other. Except in Sardinia, 

 where it is somewhat higher, sihca is about the same in all, and the 

 figures for the other constituents present close analogies with each 

 other. This is especially well seen in those for the oxides of iron, 

 ferrous oxide largely predominating over ferric, and those for titanium 

 dioxide, the figures for this constituent, which reach a maximum at 

 Pantelleria, being the highest known to me for any such large series of 

 rocks. Also these basalts are highly dosodic, and in this respect in 

 marked contrast to the salfemic rocks of the Italian peninsula, in 

 which potash is abundant and is greatly in excess over soda, giving 

 rise to the highly leucitic rocks for which the Bolsena- Vesuvius line 

 of volcanoes is so famous. 



While the general resemblance, and hence the probable genetic 

 connection, between the basalts of Linosa, Pantelleria, Sardinia, and 

 Catalonia are thus clear, it is noteworthy that the general monotony 

 of the lavas of Linosa is in marked contrast with the conditions that 

 obtain on the neighboring island of Pantelleria, as well as on Sardinia. 

 On these two islands the earlier eruptions were of highly salic rocks, 

 phonoHtes, trachytes, and rhyolites in the older classifications, being 

 followed by, and the era of vulcanicity closing with, the eruption of 



I H. S. Washington, Quarterly Journal of the Geological Society, Vol. LXIII, 

 1907, p. 69. 



