502 abstracts: geology 



viscosity of the melt. Cones 5 to 27 are made up of four oxides. It 

 is possible to discuss them, however, as a three-component system of 

 orthoclase, calcium silicate, and aluminum silicate, with excess silica as 

 a relatively inactive addition. In this system, as in the foregoing, the 

 control exercised by the low-melting eutectics upon the indications of 

 the cones is well brought out. R. B. S. 



GEOLOGY. — Are quantitative physico-chemical studies of rocks prac- 

 ticable? Arthur L. Day, Comptes Rendus Congres Interna- 

 tional G^ologique XI, Stockholm, 1910. Vol. II, pp. 965-967. 

 An address before the Section on Mineralogy and Petrography of 

 the Eleventh International Congress of Geologists, in which an effort 

 was made to show by reference to recent laboratory studies of simple 

 mineral relations, using physico-chemical methods, that these methods 

 must eventually find application in the study of the very complicated 

 mineral systems (the igneous rocks) also. A. L. D. 



GEOLOGY. — The volcanoes and rocks of Pantelleria. Henry S. Wash- 

 ington. J. Geol., 21: 653-670. 1913. 



Ths island of Pantelleria was studied in September, 1905, and the 

 paper describes both the volcanic structure and the petrography of the 

 very interesting lavas. 



Pantelleria (which lies about half-way between Tunis and Malta) is 

 entirely volcanic. It consists of an early, large cone, composed of 

 trachytes and pantellerites. After a large explosive caldera was formed 

 in this, a second volcanic phase began, consisting of the building up of a 

 trachyte core within the caldera. Later this was faulted and a large 

 block tilted down, smaller cones and flows of glassy pantellerite being 

 poured out about this. Volcanism ceased with the formation of many 

 small basaltic cones on the flanks of the earliest cone. 



The important lavas are described in great detail, seventeen complete 

 chemical analyses having been made. The trachytes and pantellerites 

 are interesting because they carry abundantly well developed crystal 

 of soda-microcline, an unusual feldspar, the crystals of which are to 

 be investigated optically and chemically later. The latter rocks are 

 also noteworthy for their content in the rare, triclinic, sodic amphibole, 

 cossyrite. The basalts are of a common type, but their occurrence here 

 in connection with such highly sodic rocks is of interest. 



The relations of the lavas to the volcanism were examined, and there 

 is a probable connection between the successive changes in the magma 

 and the phases of volcanicity, a feature apparently here recognized for 



