MINERALOGY AND PETROGRAPHY/ 
Petrographical News.— Dr. G. H. Williams' has identi- 
fied upon the island of Fernando de Noronha, the following 
rock types : hornblende-trachyte, trachyte glass, hornblende^ 
andesite, phonolite, nepheline rocks, augitite, limburgite and 
basaltic bombs and tuffs. In the phonolites, aegerine occurs 
both in porphyritic cry.stals and in the groundmass. In the 
crystals of the groundmass the inclination of the axis of great- 
est elasticity to the vertical axis is 7^ 42—16^. Their pleo- 
chroism is ^ = green, A = green, C = yellow. Among the 
nephelme rocks are basanites, dolerites and basalts. In the 
dolerites are brownish-red augite crystals which are distinctly 
pleochroic in reddish-brown and greenish-yellow tints. They 
are zonarly developed with the exterior zones more highly 
colored than the interior ones.— A recent article by E. S. 
Dana^ in the petrography of the Sandwich Islands is so full of 
mterestmg statements that a brief review of it is very un- 
satisfactory. The lavas of Mauna Loa and of Kelauea are of 
the same general character. They are basalts and oHvine- 
basa ts m numerous varieties. A fine-grained clinkstone-like 
basalt from Loa is remarkable for the beautiful feather-like 
groupmgs of augite microlites discovered in all specimens ex- 
amined. Many of the augite microlites are intergrown with 
lath-shaped crystals of plagioclase, the two minerals radiat- 
ing from a common center, and the latter often capping the 
tufts of the former. The olivine-basalt from the same crater 
contains many crystals of olivine in peculiar forms, some of 
which are slender acicular crystals elongated in the direction 
of their c axes. They often possess an unusually deep green 
color, when they show strong pleochroism. In the Mt. Loa 
lava streams are caverns from whose walls delicate stalactites 
of lava project. These are described by the author in great 
detail and are pictured with great minuteness. The stalactites- 
are often solid throughout and possess a concentric structure. 
They are crystalline, except on the outside, where they are 
covered with a thin coating of glass, transversely marked with 
fine flowage lines. Frequently a large portion of the volume of a 
stalactite consists of cavities, whose walls are lined with large 
rhombic scales of clear plagioclase,needIes of augite and octhedra 
» Edited by Dr. W. S. Bayley, Colby University, Waterville, Me. 
Am. Jour. Set. March, 1889, p. 178. 
» lb. June, 1889, p. 441. 
