1897] SOME NEW BOOKS 279 



appending his own description of the American Kimberlites. Ashe 

 slates in the preface that he has purposely avoided all reference to more 

 recent literature, the reader musl he content to miss any allusion to 

 the occni'rence of diamond in meteorites, although the resemblance 

 hetween Kimberlite and certain meteorites is frequently mentioned, 

 neither will any account he found of recent experiments upon the 



solvent action of the blue ground u] diamond, or of the artificial 



production of the mineral. 



For these reasons the hook can only he regarded as a publication 

 cf 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. Mieks. 



Landslips. 



REroKT ex the Geological Structure and Stability 01 the Hill-Slopes around 

 Naini Tal. Y>y 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 a Heeling 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 stand} >oint. 



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 penological 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 



