March 13, 1913] 



NATURE 



29 



Finally, we know little more than before of the 

 nature of the final products of radio-active trans- 

 formations. In the case of radium, we have, indeed, 

 Strong indirect evidence that lead is the product, 

 but direct evidence is still wanting. The recent 

 investigations of Prof. Rutherford's school on 

 "lateral disintegration," i.e. the formation of col- 

 lateral branches of descent, make it not improb- 

 able that more than one final product of thorium 

 exists. It may be hoped that now that powerful 

 mesothorium preparations are produced com- 

 mercially, a direct chemical investigation of these 

 final products may eventually prove feasible. 

 Each such final product identified may be expected 

 to form a link connecting up common elements 

 with the scheme of radio-active evolution. The 

 earl)- hopes of bringing these elements into the 

 scheme have been disappointed. The /3 radiation 

 of potassium and rubidium remain isolated and 

 perplexing facts. It may be that the studies now 

 so eagerly pursued on the role of )3 rays in the 

 more rapid changes associated with the radium 

 series will afford a clue. 



The principal focus of interest at the present 

 time is indeed in connection with the /3 and y rays. 

 The- discovery of v. Baeyer, Hahn, and Meitner 

 that the yS rays from certain radio-active bodies 

 can, by improved technique, be resolved into a 

 line spectrum by the magnet has given the lead 

 which was needed, and now we begin to see order 

 and definiteness where all appeared before to be 

 hopelessly involved. 



In this subject, as in all others which have 

 arrived at any maturity, the labour of keeping 

 abreast of the literature becomes increasingly 

 heavy, and the value of a complete and authorita- 

 tive treatise up to date proportionately great. 

 Even more gratitude will be felt to the author 

 by workers in this field for the present work than 

 for its predecessors. R. J. Strutt. 



MAP PROJECTIONS. 

 Map Projections. By Arthur R. Hinks. Pp. 

 xii+126. (Cambridge: University Press, 1912.) 

 Price 55. net. 



NOTWITHSTANDING the large amount of 

 surveying which has been done in this 

 country and throughout the Empire, there are few 

 works in English which treat of the various ways 

 in which portions of the earth's surface may be 

 .most conveniently and correctly represented on the 

 plane surface of a map. The subject has been 

 treated partially by several eminent mathe- 

 maticians, and valuable summaries occur in some 

 encyclopaedias, but we do not in this country 

 possess any works such as those by Germain, 

 Tissot, Hammer, and others. There are also 

 NO. 2263, VOL. 91] 



man}- works of a less advanced type which are 

 available to Continental geographers, but this 

 class, too, is very insufficiently represented here. 

 We therefore welcome the appearance of the pre- 

 sent volume, in which the subject is treated clearly 

 and in a manner which makes but small demand 

 upon the mathematical training of the geographer, 

 while at the same time the important points in any 

 projection, suitability for special purposes, and 

 facility of construction are. given 

 prominence. 



After indicating the inevitable limitations of all 

 projections, in representing length, area, and shape 

 of any portion of the earth's surface, the author 

 reviews the principal systems, and here the ques- 

 tion of nomenclature has to be faced. There is as 

 yet no general agreement in this matter, and the 

 same projections are differently named bv different 

 writers, and in different counties. In the present 

 work it is laid down that the first name of a title 

 should describe the method of construction, a 

 second name should indicate its principal quality, 

 while the author's or introducer's name may be 

 added in the case of projections which are specially 

 associated with any individual. But even this 

 arrangement cannot as yet be conveniently used in 

 all cases, and several well-known projections are 

 referred to by their usual names. 



This difficulty of a suitable classification cer- 

 tainly increases the difficulties of the beginner, so 

 that a tabular statement of the principal projec- 

 tions in this part of the book would be a useful 

 addition. Conical, cylindrical and zenithal, as 

 well as certain conventional projections, are well 

 described and clearly explained, their special ad- 

 vantages and points of weakness being indicated. 

 A chapter on the projections in actual use is an in- 

 structive addition, especially as at the present 

 time there is much more activity in selecting the 

 most suitable projections, both for wall-maps and 

 for atlas maps, than was formerly the case. . 



The chapter on the simple mathematics of pro- 

 jections treats of the theory of each particular 

 case, and discusses the errors which may arise in 

 its use under different conditions. Several actual 

 examples are worked out, so as to show the pro- 

 cedure in a particular case. The present volume 

 will be of great use to all geographers, 

 and should pave the way for a more serious 

 study of cartography on scientific lines 

 than yet generally obtains. Great care and 

 labour are expended on the measurement of 

 various regions in order to produce trustworthy 

 surveys, and the utilisation of the results should be 

 based on sound cartographical principles, and in 

 such work this book will be a valuable assistance. 



H. G. L. 



