Brief Notices. 477 
a nearly constant direction, but at intervals they are subject to abrupt 
changes of direction so as to form a series of zigzags with sharp 
elbows. In places the faults run in parallel lines, the ends over- 
lapping for short distances. All scarps, which are not much worn 
away, are steeply inclined and appear to be the continuations of nearly 
vertical faults. The highest measured vertical displacement along any 
scarp is 23 feet. Abrupt variations, and even reversal in throw are, 
however, occasionally seen. Horizontal displacements were also 
observed, though the evidence of such displacements is now almost 
obliterated. One of 15 feet towards the north was measured by 
Gilbert eleven years after the earthquake, and another of 9 feet was 
photographed by Mr. Johnson. 
CD: 
Il1.—Brier Notices. 
1. ‘Tar Sanp-Dunzs or tHE Lisyan Desrrtr’’ are described and 
illustrated by Mr. H. J. Llewellyn Beadnell (Geograph. Journ., Apvril, 
1910). In his opinion the material has been derived from the 
arenaceous formations of post-Middle Eocene age that lie to the north. 
The dunes consist mainly of silica, but in places they contain rather 
more than 7 per cent. of limestone granules. As the author remarks, 
**In some localities extensive and prosperous settlements have been 
overwhelmed and blotted out of existence, while in others the sand 
and dust-laden winds have been of positive benefit to the inhabitants. 
In the south part of the oasis of Kharga, for instance, broad terraces 
of cultivable loam have been gradually built up in the neighbourhood 
of the wells, the deposition of the wind-borne material being encouraged 
on account of its valuable fertilizing properties.’’ The subject is 
therefore of considerable economic importance as well as scientific 
interest. The author’s observations show that the dunes progress 
steadily southwards at an average rate of 15 or 16 metres a year. 
2. LANDSLIDES In THE San Juan Mountains, Cotorapo, form the 
subject of a memoir by Mr. Ernest Howe (Professional Paper 67, 
U.S. Geol. Survey, Washington, 1907). It is well illustrated, and 
contains much information of general interest and importance. 
The topography of the San Juan Mountains is described as ‘‘ that of 
a dissected and glaciated plateau of more or less horizontally bedded 
voleanic rocks resting upon a foundation of sedimentary rocks”’. The 
oldest rocks, which are pre-Cambrian, are covered unconformably by 
various Paleozoic and Mesozoic formations, and by the Telluride 
conglomerate that is perhaps of Eocene age. The Tertiary volcanic 
rocks, with an aggregate thickness of ‘‘ many thousands of feet’’ in 
the central part of the mountains, rest on the Telluride conglomerate 
or on a floor of older rocks, the dip of which is southerly, westerly, or 
northerly. Various forms of rock-falls, landslips, and soil-slips are 
described, all the rocks being lable to be affected. The superficial 
movements of the ground comprise earth-slides or soil-slips, mud-flows, 
and talus slumps. Other movements,’ though less common, are due 
to movement along bedding-planes in the direction of the dip. The 
primary jointing and secondary shattering of the rocks has led to 
