PETROLOGY: H. 5. WASHINGTON 
577 
analyses of rocks from all over the globe. To avoid complications due 
to the presence of considerable lime, a subject for further investigation, 
only peralkalic and some domalkalic rocks were selected, chiefly among 
the perpotassic, dopotassic, and persodic subrangs. The analyses be- 
longing to the sodipotassic and dosodic subrangs are so numerous that 
only a very few of the many available were used. These analyses repre- 
sent rocks from Greenland, Canada, Montana, Colorado, Wyoming, 
MgO 
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Scotland, Norway, Finland, Bohemia, Italy, Madagascar, Celebes, 
Africa, Australia, Antartica and other localities, so that, as a whole, 
variations due to regional peculiarities are eliminated. 
It may be added that the silica percentages of the rocks represented 
by these analyses vary from 39.24 to 73.68, thus covering nearly the 
entire range. 
The clustering in a narrow band, extending diagonally from high 
soda and iron in the lower left quadrant, to high potash and magnesia 
