ITALIAN PETROLOGICAL SKETCHES 363 



NOTES TO TABLE III. 



1. Monte San Vito, Bracciano, H. S. Washington anal. 



2. Monte San Vito, Bracciano, A. Rohrig anal., JouR. Geol., V, 49, 1897. 



3. Monte Cucco, Cerveteri, H. S. Washington anal., JoUR. Geol., V, 49, 1897. 



4. Castle Hill, Tolfa, H. S. Washington anal., JouR. Geol., V, 49, 1897. 



5. Tolfa, vom Rath., Zeit. d. d. geol. Ges., XVIII, 596, 1866. 



6. Monte .\miata, mean of 7 analyses, J. F. Williams, Neu. Jahrb. B. B., V. 

 446, 1887. 



7. Campiglia, Tuscany, vom Rath, loc. cit., 640. 



8. Campiglia, Dalmer, Neu. Jahrb., 1887, II, 213. 



9. Sassoforte, Rocca Strada, Matteucci, Boll. com. geol. ital., 285, 1890. 

 10. Torniella, Rocca Strada, Matteucci, Boll. soc. geol. ital., X, 677, 1891. 



acter of the plagioclase. Some of the analyses by Bunsen 

 which Hartung gives are very similar to those of Tables I and 

 II and indicate that it is basic. It is probable that similar rocks 

 occur on Madeira,' and Renard^ describes andesitic trachytes 

 from Teneriffe and Ascension which may also belong here. 



A group of rocks apparently resembling the Italian trachy- 

 dolerites from near Buda-Pesth is described by A. Koch 3 as 

 "labradorite-trachytes." They are composed of augite, horn- 

 blende, and biotite, and occasionally garnet, with labradorite 

 (analyzed) as phenocrysts, and orthoclase only in the ground- 

 mass. The analyses much resemble those of the Italian trachy- 

 dolerites, silica ranging from 52 to 67 per cent, and lime from 

 7 to 2, though magnesia is very low. Alkalies are much lower on 

 the whole, but still higher than in normal andesites, and with 

 potash predominating over soda. 



The most interesting group, however, to compare with the 

 Italian rocks is that of the absarokite-banakite series from the 

 Yellowstone Park recently described by Iddings,'* the rocks of 

 which closely resemble those of the ciminite-toscanite series. 

 The American rocks are similarly characterized by the presence 

 of orthoclase and labradorite, with augite as the most prominent 

 ferromagnesian mineral. The frequent occurrence of borders of 



' Hartung, Madeira und Porto Santo, Leipzig, 1864. 

 "Renard, Petrology of Oceanic Islands, London, 1890, 7, 23. 

 3 Koch, Zeit. d. d. geol. Gesell., XXVIII, 293, 1876. 

 BIDDINGS, Jour. Geol., Ill, 935, 1895. 



