282 Reviews—Lead Ores. 
Srimangal to a distance of 30 miles from that place, a settlement of 
from 14 to 9 inches has occurred. The author concludes that 
“there is little doubt that the earthquake was due to subsidence 
along the southern side of a normal fault cutting the rocks below 
the alluvium of the Sylhet district, and situated approximately 
under the major axis of the epicentral area”. In Dr. Stuart the 
Geological Survey of India clearly possesses an officer who may 
be expected to deal adequately with the more interesting earth- 
quakes which will probably occur before his term of service ends. 
Cs 
Leap Ores. By T.C. F. Hauu. Imperial Institute Monographs on 
Mineral Resources. 127 pp., with a map and two diagrams. 
London: John Murray, 1921. 6s. net. 
ee genesis and mineralogy of the ores of lead is a subject cf 
great interest and importance in itself, and it also forms part of 
a much larger question, namely, the existence of a definite generalized 
succession in depth of primary ore-zones. This is evidently of great 
economic importance as well as of much scientific interest, if it can 
be established, owing to its bearing on the problem of a possible 
change in the metal-content of ore-deposits when followed down- 
wards. Evidence is rapidly accumulating that such a definite 
succession will in all probability eventually be established, and the 
facts so clearly stated by the author of this memoir will doubtless 
be of very great assistance in clearing up the question. It is here 
demonstrated that in a normal lead-zinc-silver deposit the silver- 
content is highest at the top, while in depth ore with dominant lead 
commonly gives place to zinc. Whether this in its turn should 
give place to copper, as is believed by many, still remains to be 
proved, though there is a considerable mass of evidence in favour of 
this idea. 
This memoir follows the lines laid down in the preceding members 
of the series, and the author has made excellent use of the large 
amount of information available, preserving a due balance and 
bringing out the points of special interest. The information given 
is clear, up to date, and concisely expressed, while the views stated 
on the origin of lead ores, in many cases a subject of controversy, 
are fair and temperate, as might be expected from the author’s wide 
practical experience. He is to be congratulated on having well 
performed a somewhat difficult task. 
GroLocy or Mesopotamia AND Its BorDERLANDS. Compiled by 
the Geographical Section of the Naval Intelligence Division, 
Naval Staff, Admiralty. 116 pp., with 5 maps and 9 figures. 
Stationery Office, n.d. Price, 5s. 
HIS is, we believe, the first comprehensive summary of the 
geology of a little-known part of the world. In addition to 
the geology of Mesopotamia, the book contains much information 
