572 Reviews—Prismatic Structure in Igneous Rocks. 
«& 
Ii.—Tyrrs or Prismatic SrrucrurE in Icneous Rocxs. Journ. 
Geol., vol. xxiv, pp. 215-34, 1916. 
(J\HERE are several types of prismatic structure, due to different 
causes. Of these the most important are attributed to (1) thermal 
contraction in the crystallized rock, (2) convectional circulation of 
the still liquid magma, (3) internal expansion. The study of the 
prismatic structures in rock-masses may yield useful information as 
to the conditions under which the rock was formed: since quantitative 
data are very scarce, it is highly desirable that experimental work in 
this direction should be carried out; this would necessitate the 
handling of larger masses of rock than are generally dealt with in 
laboratory experiments. It is probable that much could be learned 
from a careful study of such structures in the field. 
R. H, RB. 
JIi.—Tuer Age or tae Kitrarney Granite. Department of Mines, 
Canada, Museum Bulletin No. 22, 1916. 
N this paper Mr. W. H. Collins brings forward evidence to show 
that the Killarney batholith on the north side of Lake Huron is 
intrusive into sediments of the Bruce and Cobalt series of the 
Huronian system. These have undergone a very high degree of 
deformation and metamorphism, but their correlation with the more 
normal rocks is established. The granite is not foliated and 
approaches a syenite in composition, owing to scarcity of quartz, and 
it contains recognizable xenoliths of the Espanola quartzite and other 
rocks, thus establishing its post-Huronian age. The disturbance and 
intrusion were completed long before Ordovician time, and must 
therefore be regarded as belonging to the later pre-Cambrian. 
RE 
1V.—Tue Rocks anp Minerats or tHE Croypon ReeronaL SurvEY 
ArEA. By G. M. Davirs. Proc. and Trans. Croydon Nat. Hist. 
and Scient. Soc., 1915-16, pp. 53-96. 
OR some years past this society has been conducting a nes 
survey of Kast Surrey and West Kent. The results of much 
patient work on the rocks of the district are here presented. The 
methods adopted are based on ‘panning’ of the material with 
subsequent separation in heavy liquids, and the data obtained are 
given in.a quantitative form. The minerals found are those usually 
present in sedimentary rocks of all ages, and it is clear that there 
’ has in all cases been a passage of mineral grains from one bed to 
another, so that there is less variation in composition than might be 
expected. Andalusite is found to be fairly common in Cretaceous 
strata as well as in the Tertiary sands, while the occurrence of 
monazite is of considerable interest. As might be expected, zircon, 
tourmaline, and kyanite are almost universally present in the heavy 
residues, while staurolite and garnet are almost equally common. 
R. H. BR. 
