1896] Petrography. 815 
comprise volcanic ashes, gypsiferous clays and bituminous shales, the 
last named of which were regarded by Lawson as tuffs. The present 
author declares them to be organic deposits. The igneous rocks 
which penetrate these beds are all basic. They include gabbros, 
peridotites, basalts, diabases and rocks similar to those heretofore de- 
scribed as analcite diabases. These latter are all now considered by 
the author as representing the otherwise practically unknown type of 
the teschenites. The augitic variety of this rock has the general 
structure of the diabases, in which are large poikilitic plates of augite. 
Between the diabasic constituents are polyhedral grains of analcite, 
and, in what appear to have been cavities in the rock-mass, are little 
groups of crystals and crystalline masses of the same mineral. The pla- 
gioclase in the rock is all zonal with nuclei of labrodorite surrounded 
by concentric zones of a more and more acid feldspar, the peripheral 
one being albite. An analysis of a coarse grained specimen gave : 
SiO, Al,O, FeO, FeO CaO MgO K,O Na,O P,O, Ign. Total 
49.61 19.18 2.12 5.01 10.05 4.94 1.04 5.62 .27 3.55=101.39 
which corresponds very nearly to 43.3 per cent feldspar, with a density 
of 2.57, 32.3 per cent augite, 20 per cent analcite, 4 per cent magnetite 
and .04 per cent apatite. All of the analcite is supposed to be an alter- 
ation product of nepheline. 
The basalts of the region include two types. One is the usual variety 
and the other an amygdaloidal and spheroidal variety that is intruded 
by diabases and diabasic gabbros. These last named rocks grade into 
one another. Both contain hornblende, some of which is regarded as 
secondary and some as primary. In addition to the diabasic-gabbros 
there are others associated with peridotites (and serpentines) in such a 
manner that both rocks are regarded as differentiated products of the 
same magma. The gabbro is sometimes massive. At other times it is 
possessed of a gneissic structure, often attended by a striping produced 
by the alternation of augitic and feldspathic bands. The structure is 
concluded, after study, to be the result of stretching. 
Among the other basic rocks identified in the gabbro-peridotite com- 
plex are anorthosites, diorites, norites, lherzolites, picrites, saxonites, 
wehrlites, dunites and pyroxenites. Each type is well described and a 
discussion of the banding noticed in many of them is given in some 
detail. 
Leucite-Basanites of Vulcanello.—After studying carefully 
the rocks on Vulcanello in the Lispari Islands, Bäckström’ concludes 
* Geol. För. i Stockh. Férhanl., XVIII, p: 155. 
