Review of Recent Geological Literature. 57 
ceding rocks. These very regular zones indicate considerable variation 
in composition which it is easy to individualize by reason of the almost 
constant presence of Carlsbad and albite twinning. One crystal ob- 
served, presented in its periphyry zone, perpendicular to the bisectrix 
Ng extinctions of 24° (labradorite with 55 per cent of anorthite) and 
at the centre an extinction of 51°, and the latter ought therefore to be 
classed with almost pure anorthite. 
"The microlites are themselves more basic, and exceed 20°. They 
are often accompanied by microlites of augite and of hypersthene. The 
study of a large number of specimens from the vicinity of Macouba, 
from the rivers Laillet, La Garde, and of blocks obtained in the con- 
glomerates of the same regions, causes me to believe that there exists 
a continuous series between these andesytes and these labradorytes. 
"Certain ones of the labradorytes contain lio augite, but are rich in 
phenocrysts of ophitic hornblende. A homogeneous inclusion shows 
itself to be constituted of a basic dioryte (labrador-bytownite, horn- 
blende, hypersthene, augite) which ought to be considered a-s a deep- 
seated form of the labradorytes. 
"Atigiiic labradorytes. In conclusion there is reason to cite several 
rocks having a basaltic facies which are augitic labradorytes, with or 
without phenocrysts of basic plagioclase and of olivine. These are with- 
out phenocrysts of pyroxene (Fort de France). 
"The above summary description shows that the volcanic rocks 
of Martinique constitute a petrographic series remarkably distinct, ccm.- 
prising rocks with free quartz (dacytes), rocks without quartz which by 
order of their increasing basicity are andesytes and labradorytes. Their 
common characteristic is their common essential element, a rhombic 
pyroxene, accompanied frequently by augite and by hornblende. The 
whole series is remarkable for the abundance of plagioclase phenocrysts. 
These are rarely homogeneous, but present the most beautiful examples 
that could be imagined of regular zones formed of differing composition. 
"To which of these petrographic types is it necessary to refer the 
products ejected to-day by Mont Pelee? We have as yet very little in- 
formation on this point. Nevertheless the ashes that fell on the night 
of the 3d and 4th of May, the only ones that as yet we possess, de- 
scribed by Michel Levy at a previous meeting, have a mineralogic com- 
position which approaches the hypersthene andesytes described above. 
• They are very similar to a specimen of the collection of the Museum 
from the eruption of August 5th, 1851, and obtained in the form of a 
coating on a tree. Yet another specimen, of coarser ash, of 1851. is 
rich in fragments of hornblende. (May 26. 1902.)" 
In a later contribution to Martinique (June 2, 1902) Prof. Lacroix 
has instituted a comparison between the ash of Mont Pelee of 1851, and 
the ash of the present eruption, and states that they differ very little, 
being very similar also to the ejecta of Mt. Shasta, in California, as de- 
termined by Hague and Iddings. They are hypersthene andesytes. no- 
tably less acid than those of Santorin (1866) or of Krakatoa, richer in 
alkalies, and poorer in alumina, magnesia and in lime. n. h. w. 
