May 5, 1921] 



NATURE 



29^ 



brought about by the war, and it is one of many 

 owing their appearance to the same cause. 



Part i. deals with map-reading, and the surveys 

 •of the United States, France, and Britain are 

 represented in the maps used as illustrations ; con- 

 tours and elevations, direction, scale, sections and 

 profiles, slopes, visibility problems, and grids are 

 successively dealt with. Part ii. is concerned wuth 

 the methods of making sketch-maps and field 

 sketches. The instructions for both the making 

 and interpretation of maps are clear and concise, 

 and there is a useful appendix giving a descriptive 

 list of the principal topographic maps of the 

 •world. 



(2) Miss Newbigin has produced a very read- 

 able and suggestive little volume. Following a 

 _general introduction indicating th^ difficulties 

 which the uninitiated may encounter when con- 

 fronted with the problem of eliciting desired in- 

 formation from an Ordnance map, and indicating 

 the many and varied uses to which such a map 

 may be put by those properly instructed in its 



mysteries, the author devotes a chapter to methods 

 of studying the maps with and without extraneous 

 aids, such as photographs. Curiously enough, no 

 mention is made of the possible use of photo- 

 graphs taken from the air in connection with the 

 study of Ordnance maps, though the fact that such 

 photographs are not, as yet, generally available 

 may account for the omission. 



The main part of the book is made up of de- 

 scriptions of selected sheets of the i-in. survey 

 of Britain, and these are well worked out and of 

 much interest as showing the very varied deduc- 

 tions which may be made from the study of a 

 -detailed map. 



Much is said of the geological structure of the 

 country, but it is to be feared that, in the absence 

 of geological training on the part of the student, 

 and in too many cases on the part of the teacher 

 also, any geological deductions made merely from 

 a study of the configuratten of the ground as 

 depicted in the Ordnance maps will be of but little 

 value, and, if relied upon, may give rise to 

 erroneous impressions. Even in the case of 

 Pleistocene geology the reviewer knows only too 

 well that deductions with regard to details of 

 glacial geology drawn from a study of contours 

 have frequently to be abandoned when the matter 

 is studied in the field ; and though such deductions 

 may be useful in the formation of tentative hypo- 

 theses by the investigator, they Would seem to be 

 somewhat dangerous tools to place in the hands 

 of the novice. 



(3) The methods advocated by ' l^r.' fiarker, 

 though rw)t new, are developed tcr ian '^unusual 



NO. 2688, VOL. 167] 



extent, and many applications of great interest are 

 elaborated. He shows that, by the reduction of 

 both the slope of the ground and the dip of the 

 strata to "gradients," it is possible to gain much 

 information with regard to the thickness of beds 

 or formations and the general structure of an 

 area depicted upon a map without the use of the 

 protractor. 



The surface gradient is determined in the usual 

 way by measuring the distances between contour 

 lines, and that of the stratum under consideration 

 by determining the strike by joining points of 

 equal altitude on the outcrop, and then drawing 

 parallel strike lines through points where the out- 

 crop crosses successive contour lines. These 

 strike lines will be separated by the same vertical 

 interval as the contour lines, and the stratum- 

 gradient obtained by measuring the distance be- 

 tween contiguous strike lines. 



The methods are illustrated by a number df 

 interesting and varied examples on a scale of 

 6 in. to a mile, and for maps on this scale with 

 numerous contour lines they are readily applic- 

 able ; but in the case of smaller scales, such as 

 the I -in. maps most generally in use in this 

 country, much difficulty would attend their use, 

 while in the absence of contour lines they are, of 

 course, inapplicable. 



The diagrams are good and clear, but in some 

 of these, and also in parts of the letterpress, 

 lucidity has been to some extent sacrificed to 

 the exigencies of space. Thus in paragraph 23 

 and the accompanying Fig. 18, in which the 

 reader is for the first time introduced to an " un- 

 conformable sequence," the unconformity is com- 

 plicated by. "overlap." 



As an aid to teachers or in the hands of senior 

 students or engineers, the methods advocated 

 should prove highly instructive, but the reviewer 

 feels that they do not form an adequate substitute 

 for those- more generally in use, and would not be 

 readily grasped by the average junior student. 



Our Bookshelf. 



Zoology: An Elementary Text-hook. By Sir A. E. 

 Shipley and Prof. E. W. MacBride. Fourth 

 edition. (Cambridge Zoological Series.) 



Pp. XX -f 752. (Cambridge: At the University 

 Press, 1920.) 205. net. 



Five years have passed since the third edition of 

 this now well-known text-book appeared, and the 

 authors have taken advantage of the opportunity 

 offered by the call for a new edition to place at 

 their readers' disposal some facts and inferences 

 due to certain recent researches. Thus, in the 

 account of Amoeba, Jennings's view that the 



