July 8, 1920] 



NATURE 



579 



value. His remaining chapters deal briefly with 

 schemes of afforestation, financial returns, trees 

 for planting-, the use of the unemployed in forestry 

 work, the transport of timber, etc. There is 

 nofhing novel, and a good deal that is debatable, 

 in his treatment of these subjects. 



(4) Dr. Rankin's "Manual of Tree. Diseases " is 

 the first American text-book on the subject. In- 

 juries caused by insects or other animals are not 

 included. The first four chapters treat of general 

 diseases, such as many species are liable to, and 

 those affecting seedlings, leaves, stem and 

 branches, and roots are successively dealt with. 

 The main part of the book describes the diseases 

 which attack various groups of trees, beginning 

 with alders and ending with willows. Chapters 

 on tree surgery and on spraying conclude the 

 volume, which is fairly well illustrated. Exact 

 and copious references to the literature of the 

 subject are a useful feature. * This manual will 

 be of considerable use in Great Britain, although 

 the diseases occurring here and in America are 

 often different. The account (p. 90) of Keithia 

 thujina, a dangerous fungus which has recently 

 appeared in England and Ireland on the valuable 

 forest tree. Thuya gigantea, is of considerable 

 interest. In America it is essentially a disease 

 of seedlings, often killing large numbers of those 

 less than four years old. Preliminary experi- 

 ments indicate that soap-Bordeaux mixture 

 applied every ten days in autumn will greatly 

 reduce the infection. 



(5)-(8) These four maps are attractive in 

 appearance, and will prove useful to merchants 

 and teachers, as they show approximately the 

 districts which yield the more important com- 

 mercial timbers. Their scientific value is 

 impaired by the fact that in a considerable 

 number of species the areas of distribution are 

 incorrect, and the names erroneous or confusing. 

 For example, the small map of Old World larch 

 is incorrect. European larch does not occur, as 

 depicted, in the Pyrenees, Apennines, Serbia, 

 Bulgaria, etc. The Siberian larch is wrongly 

 styled Larix dahurica, whereas it is L. sibirica 

 which occupies northern Russia and Siberia west 

 of Lake Baikal. L. hptohpis, which is restricted 

 to Hondo, in Japan, is represented as existing on 

 Hokkaido, where there is no larch, and in Man- 

 churia and Korea, where the finest L. dahurica 

 grows. The small maps might readily convey 

 more information. On the one showing Sequoia 

 and Taxodium it would be easy to add the dis- 

 tribution of important timber trees like Lawson 

 cypress, Thuya gigantea, and Western larch. 



The author has not tried to explain by notes 

 NO. 2645, VOL. 105] 



in the margin the peculiarities of popular nomen- 

 clature, such as the use of the term " boxwood " 

 for the Venezuelan Casearia praecox (see Kew 

 Bulletin, 1914, p. 214); and the application of 

 the word " cedar " to trees so different as Cedrus, 

 Cedrela, and Juniperus. One must acknowledge 

 that the construction of correct maps of distribu- 

 tion is very difficult, as accurate information on 

 some of the tropical woods is difficult to obtain. 



Our Bookshelf. 



The Natural Wealth of Britain: Its Origin and 

 Exploitation. By S. J. Duly. (The New Teach- 

 ing Series.) Pp. X4-319. (London: Hodder 

 and Sto.ughton, 1919.) Price 65. net. 

 The general scheme of this little book is de- 

 cidedly good ; it is intended to teach young people 

 how the industries and commerce of Great Britain 

 are conditioned by the geology of our island, 

 both because the geological structure determines 

 the sources from which we derive the materials 

 upon which our national existence depends, and 

 because it has produced the surface contours 

 and configuration that have decided the lines along 

 which our streams of commerce flow to-day. The 

 first portion of the book gives an outline of the 

 main principles of structural geology ; then 

 follows a section on the fundamental industries 

 based on geological structure ; and the third part 

 deals with the geographical and geological rela- 

 tions of some of our most important industrial 

 districts. 



In view of the evident educational value of the 

 plan of the book, it is all the more to be re- 

 gretted that its execution is so defective. The 

 first requisite in a text-book for young people is 

 accuracy, and in this respect the author fails 

 lamentably. A few random examples will illus- 

 trate the slipshod nature of the work. Thus the 

 author, in describing granite, states that it con- 

 sists of three constituents — quartz, felspar, and 

 " the third constituent of granite comprises all the 

 various metallic compounds." Again, a few pages 

 further on, he tells hLs readers that "sapphire, 

 ruby, aquamarine, and topaz are crystalline 

 forms of clay." 



The chapters devoted to mining are by far the 

 worst, and it is not too much to say that there 

 is scarcely a page that is not disfigured by some 

 inaccuracy of more or less importance. It is im- 

 possible to imagine anyone with any real know- 

 ledge of mining writing that "the foot-wall be- 

 neath the coal seam is cut away ... by pick- 

 axe " (the italics are the reviewer's), or that pillars 

 of coal "are sometimes left to support the roof." 

 Were it not for the numerous inaccuracies of the 

 kind indicated, this would be a most useful text- 

 book for the general reader, but, as it is, it is 

 greatly to be feared that he is as likely to pick up 

 totally false impressions as to obtain useful in- 

 formation from its pages. 



H. L. 



