Aya HENRY S. WASHINGTON 
This idea was first broached by Von Lasaulx,* and his remarks 
are of such importance that a full quotation of the passage bear- 
ing on this point may be given: 
‘“A conclusion which follows directly from the observations 
on the character of the constituents of the andesites of the Sieb- 
engebirge is this, that the less hornblende a rock holds the more 
it approaches a true augite-andesite, and the more the hornblende 
shows signs of resorption, so much the richer is the groundmass 
in finely divided magnetite. If . . . the hornblende is a con- 
stituent which has separated out of the fluid magma as one of 
the earliest at a great depth, then it would depend on how far 
the originally formed hornblende had undergone fusion and 
solution whether a rock appears in the upper regions as horn- 
blende-rich or hornblende-poor. That augite is formed out of 
the magma easily and abundantly through resorption of enclo- 
sures and the earliest crystals can likewise be shown by experience; 
on the other hand hornblende appears to have been formed in 
this manner much less often. Likewise the magnetite of the 
groundmass can be increased by refusion of small hornblende 
crystals. 
“An augite-andesite can therefore arise out of an original 
probably hornblende-andesite magma, if this remains in a state 
of liquidity so long that the hornblende which has been formed 
at a depth may be again wholly, or mostly, dissolved, and augite . 
and magnetite be formed in its place.” 
The general similarity of the views expressed in the above 
quotation as to the origin of some augite-andesites with my own 
is apparent. It must be remarked, however, that the conclusions 
are as true of biotite as of hornblende, and also that I differ 
radically from Von Lasaulx in considering that the derivative 
augites are not crystallized out of the magma from dissolved 
hornblende substance, but are due to a molecular change and 
subsequent mechanical disintegration. 
Zirkel expresses himself as against such an origin, saying 
that it would apply in any case not to the phenocrystic but only 
*VON LASAULX, op. cit., 1858. 
