1897] SOME NEW BOOKS 279 
appending his own description of the American Kimberlites. As he 
states in the preface that he has purposely avoided all reference to more 
recent literature, the reader must be content to miss any allusion to 
the occurrence of ‘diamond in meteorites, although the resemblance 
between Kimberlite and certain meteorites is frequently mentioned, 
neither will any account be found of recent experiments upon the 
solvent action of the blue ground upon diamond, or of the artificial 
production of the mineral. 
For these reasons the book can only be regarded as a publication 
of papers that should have appeared ten years ago, which, though 
interesting and important as a petrographical study, do not throw 
much light upon the vexed problem of the genesis of the diamond. 
H. A. MIgErs. 
LANDSLIPS, 
REPORT ON THE GEOLOGICAL STRUCTURE AND STABILITY OF THE HILL-SLOPES AROUND 
Naini Tau. By T. H. Holland, Officiating Superintendent, Geological Survey 
of India. Pp. viii., 85, with a map and 11 plates. Calcutta: Office of the 
Superintendent of Government Printing, India. 1897. 
THIS report shows the practical value of a thorough knowledge of the 
geological structure of a district as affecting its suitability for habita- 
tion. It is entirely a practical work, written for the guidance of 
engineers and others familiar with the locality, and treats the subject 
from a purely utilitarian standpoint. 
Naini Tal is a lake in the north-west provinces of India on the 
flanks of the Himalaya. There is a hill station located here, but the 
district suffers somewhat from the frequency of landslips. It is, 
indeed, probable that the lake owes its origin to the damming up of a 
stream by a great landslip, as was suggested by Dr Ball in 1878, 
though his views have not been universally accepted. 
The object of the investigation, of which this report is the outcome, 
was to discover the cause of the instability of the hill-slopes in the 
district, to determine the extent of the insecure sites, and to suggest 
means for increasing their stability. 
The methods adopted by the author were the following :— 
(1) On a large scale (20” to 1 mile) contoured map were inserted 
details of the distribution and petrological characters of the rocks. 
(2) The angle of repose of the rocks under different conditions was 
determined. 
(3) Cross-sections were constructed from the map showing the 
slope along the selected lines, and the portions of the rock lying out- 
side the lines of safety were determined from the angles of repose. 
The direction of the movements is shown in the report to be 
governed by the direction of the stratification planes, which in many 
areas have a dip in the same direction as the slope of the hill-sides 
but smaller in magnitude. 
The rocks most affected are shales and dolomitic sandstones, and 
the lubricant is provided by the decomposition of the rock, which is 
brought about by water percolating along the stratification planes, and 
forming in the first instance a slippery clay, and in the second a layer 
of loose sand. 
The great difference between the angle of repose of dry broken 
