THE CLASSIFICATION OF THE IGNEOUS ROCKS 21 
acid and intermediate composition have been prepared. Plate VII 
displays together the composite diagrams of the specific types 
belonging to the families which Washington* has designated as 
the trachyte, trachy-andesite, trachy-dolerite, and andesite series. 
The rhyolite diagram is a composite of nine analyses of 
rhyolites from Hungary, Ponza, the Auvergne, Nevada, and 
Colorado. The soda-rhyolite composite is compounded from 
six analyses, mainly of Wisconsin rocks soon to be described by 
C. K. Leith and the writer. The four pantellerites which furnish 
the pantellerite diagram are from the island of Pantelleria. The 
trachytes, six in number, are those of the Auvergne, Ischia, the 
Eifel, the Bohemian Mittelgebirge, and Monte Amiata; and 
the two domites were from the Auvergne. The vulcanite dia- 
gram is not a composite but an individual rock diagram made 
from the type analysis from Vulcano. The six dacite analyses 
composed were of rocks from Columbia, Guatemala, Lassen’s 
Peak, Cal., and McClellan Peak, Nev., while the seven andesite 
analyses used in preparing the andesite composite were of mica- 
and hornblende-andesites from the Eureka district, Nev.; Custer 
county, Col.; Cartagena, Spain; the Siebengebirge on the Rhine; 
Panama; and Columbia. The Toscanite, Vulsinite, and Ciminite 
analyses are the Italian ones given by Washington,’ and were 
respectively ten, ten, and eleven in number. The Banakites, 
Shoshonites, and Absarokites represented in the analyses are 
those described by Iddings3 from the Yellowstone National Park 
and numbered four, five, and five respectively. 
These specific composites are much less interesting as indi- 
cating relationships than the composites of a higher order would 
be, but they are here introduced to show that the composite 
diagram is capable of bringing out the chemical characteristics 
of rocks which differ only slightly from one another, as well as 
the characteristics of different families. 
tH. S. WASHINGTON: Italian Petrological Sketches, V. Jour. GEOL., V, p. 366. 
1897. 
2H. S. WASHINGTON: loc. cit. 
3J. P. Ipp1ines: Absarokite-Shoshonite-Banakite series, Jour. GEOL., III, pp. 935— 
959, 1895. 
