January 15, 1903] 



NA TURE 



245 



are greedy beyond expression. A European laid out 

 some cotton and coffee to dry in the sun, and when he 

 looked for it after a time the locusts had devoured it all 

 — cotton, coffee, and even the blankets on which the raw 

 material had been spread out." Since then, the locusts 

 have never left the district, and were again very destruc- 

 tive in 1898 (pp. 7, 8). 



In South-west Africa, various locust invasions are 

 noticed, from 183 1 to the present time ; and it is 

 recorded that at Barmen (in the present Orange Colony) 

 in 1866, the 



" Fussganger " (immature locusts) " not only devour all 

 the plants, green or dry, before them, but everything 

 that they can find, including linen and clothes left un- 

 protected ; for they creep into the houses even to the 

 bedrooms, and eat up everything" (p. 20). 



A pitiful story comes from Little Namaqualand in 



■873:- 



" On the morning of May 5 I held a prayer-meeting 

 to implore the Lord to send us a little rain, and to put 

 an end to the great drought and distress. In the after- 

 noon clouds actually rose, and we heard a rushing in 

 the air as if it was about to rain ; but, alas ! the noise 

 was caused by swarms of locusts, which covered the 

 whole place, and completely devoured the little dry 

 grass that was left " (pp. 21, 22). 



One is forcibly reminded of the old story of the 

 Adites, who sent a deputation to Mecca to pray for rain, 

 and were answered by a black cloud which sent forth a 

 desolating wind which exterminated the whole tribe. 



After discussing the ravages of locusts in the various 

 territories of German Africa, Dr. Sander proceeds to 

 give a full account of the habits, transformations, 

 biology, &c, of the most destructive species of African 

 locusts, and also discusses the best means of contending 

 with their ravages ; and the natural enemies of locusts 

 (birds, &c.) are also noticed. Without being overloaded 

 with illustrations, there is a suffi;iently good series in 

 the text to render the subject intelligible to the general 

 reader. An appendix contains an interesting edict of 

 Frederick the Great, ordering the destruction of locusts 

 in Prussia in 1753. Dr. Sander's maps illustrate the 

 prevalence of the pest in German East Africa from 1S97 

 to 1899, and in Cape Colony and South-western Africa 

 from 1891 to 1900. His book, though written, of course, 

 for the benefit of the German colonies in Africa, deserves 

 the most serious attention from all who are interested in 

 the welfare and prosperity of our own African posses- 

 sions. • W. F. K. 



OUR BOOK SHELF. 



Applied Mechanics for Beginners. Bv J. Duncan, 

 Wh.Ex., A.M. Inst. C.E., &c. Pp. x + 3'24. (London: 

 Macmillan and Co., Ltd., 1902.) Price is. 6d. 



With the development of the mechanical laboratory in 

 technical schools and colleges, the teaching of mechanics 

 has in recent years undergone a quiet revolution. Ex- 

 periments are no longer confined to the few made by the 

 teacher, but the students now all take a share in this 

 kind of work, which has become an important part of the 

 school or college course, being of great value, as affording 

 the training in inductive methods which in former times 

 was often neglected. 



N0 - ^Zo' VOL - 67] 



The volume under review shows the influence of these 

 prevailing conditions. A considerable portion of the 

 book is devoted to the description of laboratory ap- 

 pliances, the methods of making tests and the kind of 

 information to be got therefrom. Some of the apparatus 

 is of quite a simple character, such as a student may 

 readily make and use at home, and yet from which 

 fundamental mechanical principles can be verified and 

 illustrated in a satisfactory manner. In other cases, the 

 experiments are more elaborate ; those dealing with 

 hydraulics strike us as being particularly good. 



Another important part of a course in applied mechanics 

 is the working of many numerical examples ; here also 

 the requirements are well met, and the student is amply 

 provided with material in great variety. The answers to 

 the examples are given at the end of the volume. 



There are a few defects which may probably be 

 remedied in great measure in a future edition. The 

 diagrams are well drawn and clearly printed, but in some 

 cases the letters of reference are unfortunately too small. 

 The author is not very happy in his definitions of the 

 engineer's units of mass and force, and occasionally his 

 enunciations of fundamental principles of mechanics 

 could be improved by revision. The treatment of vectors 

 is rather weak. We should like to have seen more use 

 made of the radian measure of angles and angular 

 velocities in the many problems involving rotation. 



These faults do not detract materially from the general 

 merits of the book, which is one that can be confidently 

 recommended for the use of students who are begin- 

 ning the subject of applied mechanics and wish for 

 guidance in obtaining an experimental knowledge of the 

 foundations on which the science is built, and for an 

 account of many of its applications in the arts. 



Comp/e rendu du deuxicme Congres international des 

 Malhe'maticiens temi a Paris. 6 au 12 Aout, 1900. 

 Pp. 450. (Paris : Gauthier-Yillars, 1902 ). 



Among the innumerable congresses held at the Paris 

 Exhibition, this one dropped completely out of sight. On 

 arrival at the advertised place of meeting in the Hall of 

 Congress, it was found occupied already by some 1500 

 deaf-mutes, assembled in conclave ; naturally they could 

 give us no information. The Mathematical Congress was 

 discovered at last, on the top floor of the Sorbonne, 

 where it was left severely alone by the French professors, 

 too dignified to meet the herd of visitors on equal terms. 



The Physical Congress, held simultaneously, carried off 

 all but the mere pure mathematicians, who enjoyed them- 

 selves by reading papers to each other on arithmetic and 

 algebra, analysis and geometry, bibliography and 

 teaching methods. 



An eloquent address by M. Poincare, the president, 

 who put in an appearance at the closing ceremony, on the 

 role of intuition and logic in mathematics, an extract 

 from a lecture bv Mittag-Leffler on a page of the life 

 of Weierstrass, Hilbert's discourse on the mathematical 

 problems of the future, and communications by M. 

 Cantor on mathematical historiography and by Vito 

 Volterra on Betti, Brioschi and Casorati, these form the 

 most important part of the volume. 



Wood : a Manual 0/ the Natural History and Industrial 



Applications of the Timbers of Commerce. By G. S. 



Boulger. Pp. viii + 369. (London : Edward Arnold, 



1902.) Price 7s. 6d. net. 



The contents of this ugly volume, of heavy paper and with 



narrow margins, are more worthy of attention than its 



exterior suggests, and comprise an immense amount of 



information about the timbers of commerce from many 



points of view. That it is a compilation which would 



probably never have seen the light had not the works of 



