ala DEE fOOLINALEORNGE OL OGN- 
1) Those of concentric spheroidal form produced by foreign inclu- 
sions. : 
‘2) Those where the varioles were formed by the partial resorption 
of fragments of the locally solidified magma. : 
3) The so-called “pudding granites,’ due to a concretionary 
action. 
4) Those varioles which are primary structural forms of the magma, 
or are due to endomorphic contact action. : 
The conditions requisite for the formation of varioles are: 
1) A difference in the basicity within the magma. 
2) The cores must be near each other. 
3) There must be a difference in temperature between the core and 
the magma. 
4) The temperature must be high enough to aid resorption but not 
sufficient to permit the complete resorption of the fragments. 
While the work is occupied primarily with a study of the origin 
of macrovariolitic rocks, it is full of incidental studies of the minerals 
encountered. ‘This is especially true of zircon, the feldspars, and per- 
thitic intergrowths, while there are many suggestive points on phe- 
nomena frequently seen in quartz,:apatite, hornblende, etc. On the 
whole the work is an example of a careful, exhaustive study of a cir- 
cumscribed problem. 
EDWARD B. MATHEWS. 
On the Banded Structure of Some Tertiary Gabbros in the Isle of Skye. 
By SiR, ARCHIBALD GEIKIE and»): J. HH! VEArr. 5 @uange 
Jour. Geol. Soc., November, 1894.. Vol: 1., pp, 645-650. 
Pls. DOGV A ON EIS DO GV allie 
THE importance of this study of the Tertiary gabbros of Skye is 
twofold, as pointed out by the author: First, as a contribution to our 
knowledge of the structures which may be assumed by igneous rocks 
at the time of their solidification, or prior to their consolidation. 
Second, as an aid to the elucidation of some of the most perplexing 
problems in the study of the crystalline schists. 
The rocks described are part of the volcanic complex which forms 
the picturesque group of mountains known as the Cuillin Hills in the 
southern portion of the Isle of Skye 
a vast aggregation of indurated 
tuffs, agglomerates, lava-flows, besides intruded bodies that have broken 
