May 8, 1919] 



NATURE 



183 



T' 



canal was drawn a barricade of cilia, also loaded. 

 The canals are so set that a displacement of the 

 fluid within them accompanies every movement, 

 the rate of the displacement being registered by 

 the barricade of hair-cells set across their lumina. 

 By the introduction of a few modifications an area 

 of hair-cells was exposed to displacements of 

 fluid set up by the impact of sound-waves. 



Physiologists are only beginning to realise that 

 Bdrdny's researches on the action of the balancing 

 part of the labyrinth are at the same time throw- 

 ing a novel light on the nature and action of its 

 cochlear or auditory part. The machinery and 

 the manner in which the machine works are the 

 same in both cases — that of registering a mass 

 displacement of the contained fluid. The evolu- 

 tionary story of the ear, so far as we know it, 

 is dead against any part of the cochlea acting as 

 a resonator. A. Keith. 



MILITARY GEOLOGY AND TOPOGRAPHY. 



Military Geology and Topography : A Presentation 

 of Certain Phases of Geology, Geography, and 

 Topography for Military Purposes. Edited by 

 Herbert E. Gregory. Prepared and issued under 

 the auspices of the Division of Geology and 

 Geography, National Research Council. Pp. 

 XV + 28 1. (New Haven : Yale University Press; 

 London : Oxford University Press, 191 8.) Price 

 55. 6d. net. 



HIS work is essentially a text-book, prepared 

 with the primary intention of helping in the 

 teaching of the elements of geology and geo- 

 graphy to those about to take commissions in the 

 Army of the United States. Throughout it aims 

 at teaching first principles, avoiding technical 

 terms so far as possible. 



The first chapter gives an epitome of the types 

 of rock on the earth's surface, with such details 

 as are of interest to the engineer. This is fol- 

 lowed by a few pages on earth movements, with 

 excellent diagrams of the effects of faulting, etc. 

 The space allotted to this subject is so restricted 

 that only the most general outlines can be given. 

 The chapter ends with a "summary of engineering 

 considerations related to rocks." Chap. ii. deals 

 with rock weathering, explaining how the strata 

 mentioned in the previous chapter became altered 

 when exposed to atmospheric agents. The next 

 three chapters deal respectively with streams, 

 lakes, and water supply. Most of the information 

 contained in these chapters is such as should be 

 known by everyone who expects to live or journey 

 beyond a city where water is merely obtained 

 by turning a tap and disposed of by means of 

 drains. 



Under the heading of water supply several pages 

 are given to military requirements. In dealing 

 with the volumes of water required by an army the 

 demands from all sources — men, horses, wash- 

 ing, etc. — are added together and divided by the 

 I number of men in the unit ; the result is then 

 ^ given in gallons per soldier. The figure to-50 

 I NO. 2584, VOL. 103] 



gallons per day per soldier is thus arrived at. A 

 point which is not brought out is that a distinc- 

 tion can often be drawn between water for horses 

 and water for human consumption. Emphasis is 

 rightly laid on the importance of the time-factor 

 in military water-supply schemes. Schedules for 

 entering up details of wells, springs, etc., given 

 on pp. 152-56, are those in use by the United 

 States Geological Survey, and therefore have the 

 advantage of having been tested by actual use. 



Chap, vi., on land forms, gives, with the help 

 of excellent small diagrams, a good introduction 

 to the study of the relationship of geological 

 structure to the topography of an area. At the 

 end of the chapter is a page of military problems. 

 These are good in showing how geology should 

 be considered in conjunction with other details of 

 a military nature. Unfortunately, only a very small 

 space is devoted to this side of the subject. 



Chap. vii. will be found useful in the teaching 

 of map reading and map interpretation. The 

 chapter deals with topographical, and not geo- 

 logical, maps, but shows how the general geo- 

 logical structure of an area can often be foretold 

 by a study of the topography. The book ends 

 with short notes on various minerals, with special 

 reference to their uses in war. 



The work throughout is designed for teaching, 

 and it is in some ways unfortunate that it bears 

 the word "military " in such prominence, for the 

 book will be found to be of value to all who wish to 

 have some of the everyday practical applications 

 of geology put before them in an elementary way, 

 or to those who desire a well-illustrated text-book 

 for teaching purposes. From the military point 

 of view it should be noted that the book is 

 designed to help all oflRcers to understand the 

 elementary facts regarding the ground on which 

 they are, or expect to be, fighting. No mention, 

 however, is made of the need for a special geo- 

 logical section of the Engineers composed of ex- 

 perts who can have access to published works 

 and maps, and be in personal touch with 

 men who have worked in the area. There is no 

 doubt that much time and energy would frequently 

 have been saved during the war if all officers had 

 known the principles set forth in this book. It 

 should be borne in mind that unless expert advice 

 is obtained for the larger engineering under- 

 takings, the little knowledge which is a dangerous 

 thing may lead to the starting of impracticable 

 schemes. W. B. R. K. 



OUR BOOKSHELF. 



A Century of Science in America. With Special 



Reference to the" American Journal of Science," 



1818-1918. By Edward Salisbury Dana and 



Others. Pp. 458. (New Haven : Yale University 



Press ; London : Oxford University Press, 



1918.) Price 175. net. 



Though the "prefatory note " makes no mention 



of the fact, this handsomely produced work 



appears to be a reproduction for the library-shelf 



of the number of the American Journal of Science 



