 1886.] Mineralogy and Petrography. 641 
Opal replaces the original constituents of the rock, ‘first replacing 
the feldspar, then the augite and finally the glass base. Occasion- 
ally this silica takes the form of tridymite. Near the port of 
blende andesites were found. Ina yellowish glassy base, con- 
taining numerous microlites of feldspar, augite and grains of mag- 
netite, large porphyritic crystals of labradorite, hornblende and 
biotite occur. The hornblende often possesses the two pinacoids 
well developed. In some cases this mineral is surrounded bya 
rim of small, colorless or very light-green augite crystals, ar- 
ranged with their long axis parallel to the long axis of the horn- 
Panama canal, is an augitic labradorite containing hornblende. 
The porphyritic crystals of labradorite, augite and magnetite 
ination. Two hundred and fifty slides of specimens collected 
between the depths of 4000-5000 meters have been examined. 
By far the largest number of these are of rocks of the “ old meta- 
The most highly crystalline member of _the former is a 
pale pink-grey pegmatite,” passing through a well-defined 
graphic granite into a micropegmatite form. The less crystalline 
members of the acid series are felsites -with well-developed 
Spherulitic structure. Corroded quartzes, surrounded by the 
the “ quartz globulaire” of Fouqué and Lévy, were observed in 
a of these felsites. The more basic series is composed of à 
a ases, diorites and rocks intermediate between these, witha «` 
€w in which the author thinks he has found evidence of pe or 
Chrustschoff has just published* an 
quartz took place. These new crystals are frequently bounded ae: 
"Bulletin de l’Acad. Roy. de Belgique, 111, 2, p. 156. 
omits Rendus, cir, No. I4, P. 793- 
= Sy Magazine, May, 1886, p. 219. 
_ “Aineralogische und Petrographische Mittheilungen, vil, p. 295. 
