1889] Mineralogy and Petrography. 259 
ritic crystals of leucite, augite, plagioclase, sanidint, magne- 
tite, apatite, hauyne, nepheline and more or less olivine in a 
groundmass composed of microlites of leucite, augite and pla- 
gioclase, and a very little glass. According to the predomi- 
nance of one or the other of the constituents they are divided 
into basaltic, doleritic and tephritic varieties, and these are fur- 
ther subdivided into olivinitic and non-olivinitic sub-varieties. 
To the northeast of the Lake there is an augite-andesite 
with a zonal plagioclase in which the different zones possess very 
different extinction angles. The paper in which these rocks 
are described contains a fine series of analyses. — An interesting 
occurrence of basic concretions in the granite of Mullaghderg, 
County Donegal, Ireland, is described by Hatch.' The rock is 
a dark, coarse-grained, sphene-bearing, hornblende-granitite 
containing microcline, orthoclase and oligoclase. Sections of 
orthoclase nearly parallel to the orthopinacoid are traversed 
by two sets of strongly refracting markings parallel to the 
cleavage lines. The markings are due to the deposition of a 
mineral with an extinction of \\° in the formerly existing 
cleavage cracks. In this granite are flattened spheroids of 
three or four inches in diameter, which consist of a reddish 
granite nucleus and a zonally and radially developed periphery 
composed of plagioclase, magnetite and a little brown mica. 
A resume of the literature of spheroidal granites is given and a 
classification of the spheroids is attempted. — A second' paper 
on the dyke rocks of Anglesey is occupied with a description 
of the diabases and diabase porphyrites of the islands of 
Anglesey and Holyhead, England. A hornblende-diabase 
from a large dyke running along the east side of Holyhead 
Mountain contains a large amount of apatite, and augite crys- 
tals that have been enlarged by the addition of original horn- 
blende material.' — Dr. Bonney' regards the isolated masses of 
green sandstone occurring in the sand pits near Ightham in 
Kent, England, as having originated /;/ situ by concretionary 
action. The individual grains are connected together by chal- 
cedony and quartz, the latter forming a fringe around each 
one of the grains and the latter filling in the remaining inter- 
stices.— Dr. Hatch' records the analysis of a microgranitic ker- 
atophyre from near Rathdrum, County Wicklow, Ireland. 
^/er'Jca^Na 
Soc. 188J 
\\.^X 
e'r : Geoi! Ma 
gSne,''8i8. p. 26 
Magazine. x\ 
Magazine: F, 
!f,W', 
7- ^ 
