SAGE CLIN OL, AEGAN ANAND (MEE AMEALAYN Ar, 167 
here than in the other... CaO and Na,O are beautifully inverse 
in both, except at the acidic extremity on Santorini where they 
both drop slightly together. They also cross in these rocks, 
soda becoming higher than lime at this end. FeO and MgO 
show the same kind of parallelism, and both are inverse toward 
Al,O, throughout nearly all their length, but with the parallelism 
at the acidic end (especially between FeO and Al,O,) well shown 
in the two diagrams. The inverse variation of Al,OQ, and CaO at 
the basic end and their parallelism toward the acidic end is well 
marked in both. But the above are sufficient, and further exam- 
ination will only bring out more clearly the extremely similar 
character of the two lavas. 
It would be most interesting to draw our conclusions from 
an examination of the diagrams given as to the character of the 
original magma, but it will be better to wait until a more satis- 
factory diagram can be drawn for Santorini with, if possible, one 
of Milosand Nisyros. By studying sucha group of diagrams from 
a well defined volcanic fracture line the conclusions we might 
arrive at would be more valuable than those derived from less 
complete material. It may be worth remarking though, that, 
judging from these two examples, we can assert with much con- 
fidence that the rocks of Milos and Nisyros will be found to fur- 
nish diagrams resembling in their main features, if not in details, 
those given in this paper; that their general petrographical char- 
acters will be found to be very similar to those of the A‘gina- 
Methana region, and also that the so-called rhyolite of Milos is 
in reality a dacite. 
In conclusion, I may say that the two diagrams given here 
are sufficient to prove conclusively that not only do the eruptives. 
of A©gina-Methana and Santorini belong to the same petrograph- 
ical province, 7. e., are derived from the same main body of 
magma (which was @ priori to be expected), but that this petro- 
graphical province has a magma quite different from that of the 
*Compare the K.O lines of these diagrams with those in the diagrams of the rocks 
of the Andes and the Yellowstone National Park, where the most acid rocks are rhyo- 
lites. 
