Reviews—Topographic Maps and Sketch Mapping. 281 
A distinct metamorphic aureole surrounds the plutenic complex, 
and amongst the’ metamorphic products are andalusite and cordierite 
mica schists. 
Pneumatolytic metamorphism of the country rocks, involving the 
introduction of Na,O and TiO,, is strongly developed near the 
contact with the albite syenite. This metasomatism has resulted in 
the production of albite hornfelses consisting of a fine-grained 
mosaic of quartz, albite, chlorite, and rutile. The syenite itself has 
not escaped metasomatie alteration, the biotite of both country 
rock and igneous rock being converted into chlorite. 
The paper is furnished with seven complete rock-analyses, and 
the relations of a number of these are expressed in a variation 
diagram. The Encounter Bay suite of rocks forms an admirable 
illustration of an igneous rock series in which a_ progressive 
differentiation with increasing alkalinity is strongly emphasized. 
C. EB. TILuey. 
TopoGraPuic Maps AND SxetcH Mappine. By J. K. Fincn, C.E., 
A.M. pp. 168. John Wiley & Sons. 13s. 6d. 
yes is an elementary book on sketch mapping, and only the 
appendix will have much interest for the geologist. The latter 
consists of a descriptive list of the topographic maps of the world, 
special attention being given to the less well known, such as those 
of South America. This list will be very useful for reference, and 
apparently has been collected with considerable care by the compiler, 
F. K. Morris. 
THE SRIMANGAL EARTHQUAKE OF 8TH JULY, 1918. By Murray 
Stuart, D.Sc. Mem. Geol. Surv. India, vol. xlvi, 1920. 
pp. 1-70, 12 plates. 
Ae Srimangal earthquake of 1918 deserved the careful investiga- 
tion bestowed on it by Dr. Murray Stuart, though it is not one 
that has added much to our knowledge of earthquake-phenomena. 
The principal sections of the report are those which deal with the 
nature and effects of the shock within successive isoseismal lines, 
the analysis of the seismograms at various observatories, the 
secondary earthquake that occurred four or five minutes later with 
its epicentre near Madura in Southern India, and the results of 
the re-levelling across the epicentral area in the Balisera valley and 
in part of the Doloi valley. The depth of the focus is estimated, 
by Dutton’s method, at about 8 or 9 miles. During the winter of 
1919-20 the Trigonometrical Survey repeated a series of levels, 
first carried out in 1911-12, along the line from Silchar to Comilla, 
which crosses the epicentral area ‘nearly at right angles to its longer 
axis. A comparison of the two series of levels shows that no change 
took place in the area to the north-east of the epicentral axis, but 
that, on the other side, from the low range of hills 6 miles west of 
