NATURE 



[NOVEMBEK 8, 1894 



M. Maislre, to which he transferred himself, and again 

 crossed the Congo-Shari watershed, made friends of 

 many of the native tribes, obtained treaties in the usual 

 way, and, pushing onwards, in spite of considerable hard- 

 ships, descended one ofthetributariesof the Shari, struck 

 westwards to the Benue, and so returned by the Niger. 

 The expeditions, which were two of the most important 

 of the last few years, did much valuable work in geography 

 and natural history ; indeed, M. Brunache insinuates that 

 Dybowski was too much devoted to collecting specimens 

 to make an ideal commander. 



The book contains many interesting but unsystematic 

 notes on a number of tribes which were visited for the 

 first time by Europeans. E.\cept the Bonjios on the 

 lower .Mobangi.and the Mohammedanised natives of the 

 Sudan, they were all cannibals, eating their enemies 

 killed m battle, and occasionally their slaves. Amongst 

 all the tribes, women were well treated and consulted on 

 affairs of importance. The costume and habits of the 

 Saras, a particularly tall tribe, who inhabit the Shari 

 basin between S^and 9' N.,are described, we believe, for 

 the first time, and with such fulness and tact as only a 

 Frenchman can employ. In their country the surveys of 

 the expedition touched those of Xachtigal, who had pene- 

 trated so far southward across the Sahara, and thus com- 

 pleted the chain of modern European itineraries in West 

 Africa from the Mediterranean to the Cape of Good 

 Hope. 



A number of reproductions of sketches exhibit types 

 of the natives encountered, and specimens of their art and 

 manufactures. 



Helical Gears. By a Foreman Pattern Maker. (London : 



Whittaker and Co., 1S93.) 

 This little book belongs to " The Specialists' Series " ; it 

 is entirely of a practical nature, and deals with a subject 

 little understood by engineers who do not happen to be 

 machme-tool makers. As there is probably no other 

 text-book on this subject, the work will fill a uselul 

 purpose. The author observes that a large proporfion 

 of so-called helical gears are incorrectly made, and are 

 therefore far worse than common gears. With this obser- 

 vaiion we certainly heartily agree. Cases are known 

 where an otherwise good machme has been spoiled by 

 the use of badly designed helical gearing. 



The arrangement of the information is good. lUus- 

 traiiuns and diagrams are (reely used, so that what 

 would otherwise be difficult to understand becomes 

 clear and apparent. Patterns are clearly dealt with, 

 and their manufacture fully described. It is here 

 the hand of the practical man becomes evident. Many 

 hints are given, and instructions formulated, which 

 flavour btrongly of the " works." The author does not 

 pretend to deal with the purely theoretical side of his 

 subject, excepting in so far as the fundamental relation- 

 ships 01 the helical gears to the true screw or helix is 

 concerned. Beyond this the book is entirely of a practical 

 character, being eminently fitted to fulfil the require- 

 ments of the drawing-office and the works. N. J. L. 



The Nests and Eggs of Xon-Initigenoiis British Birds. 



By Charles Dixon. Pp. 360. (London : Chapman 



and Hall, 1894.} 

 " Tm. present work," remarks Mr. Dixon in his preface, 

 " forms the companion volume to ' The Nests and Eggs 

 of British Birds,' and renders the subject of Briti>h 

 Oology complete, so far as our knowledge now extends. 

 It deals exclusively with the nidification of the birds 

 that do not breed in the British Archipelago, but visit 

 our islands regularly in winter, pass our coasts on 

 passage, or pay them their more or less irregular visits 

 as wandercis from their normal areas of disposal." 

 Nearly two hundred species are described as belonging 

 to this clas}. For each bird, information is given as to 



NO ijo6, VOL, 51] 



the breeding area, breeding habits, range of egg coloura- 

 tion and measurement, and the diagnostic characters of 

 the eggs. In an appendix, the author states his reasons 

 for believing that the nests and eggs of the following 

 species are at present unknown to science : — Rustic 

 bunting, Pallass grey shrike, Siberian ground thrush, 

 needle-tailed swift, solitary sandpiper, Siberian pectoral 

 sandpiper, curlew sandpiper, knot, Ross's gull, great 

 shearwater, collared petrel, capped petrel. Cape petrel, 

 and white-billed diver. A list of forty species, individuals 

 of which have been said to occur within the limits of the 

 British Isles, but which Mr. Dixon regards as doubtful 

 British species, is also appended to the volume. It 

 remains for the scientific naturalist to collect some de- 

 finite information on the species enumerated in these lists. 



Commercial Geography. By E. C. K. Conner, M.A. 



Pp. 200. (London : Macinillan and Co., 1S94.) 

 CoM.MERCl.\L geography, dealing as it does with the 

 facts that aftect manufactures, commerce, and agricul- 

 ture, ought to be widely studied in a nation having such 

 pronounced shopkeeping proclivities as the English. It 

 is right and proper that those who are to be the custo- 

 dians of our trade in future should know something about 

 the manner in which physical and political surroundings 

 alVect industry and commerce, and about the conditions 

 of success in the various industrial branches. Prof. 

 Conner treats these matters in a way likely to impress 

 students. His manual is divided into three pans, the 

 respective subjects of which are (i) commercial geography 

 and its principles ; (2' the geography of the chief pro- 

 ducts and others ; (3) countries, their agriculture, indus- 

 tries, and commerce. Trustworthy statistics are plenti- 

 fully distributed throughout the book, and they serve to 

 give an idea of the relative importance of different 

 countries as regards ditierent commodities, as well as 

 being useful for reference. Of course, no student would 

 be expected to commit these tabular statements to 

 memory. If the main facts contained in this volume are 

 grasped by students intended for commercial careers, 

 British commerce will undoubtedly be benefited. 



Dynamometers and the Measurement of Power. By 

 John J. Flather, Professor of Mechanical Engineering, 

 Purdue University. (New York: John Wiley and Sons, 

 1892.) 

 A USEFUL practical treatise on this subject, in a con- 

 venient form for Technical Students, containing also the 

 mechanical theory required in the calculations. 



The author has himself carried out a notable experi- 

 ment in the measurement of the power of a lull-siied 

 American locomotive, which was jacked up, and the 

 power taken olT by heavy supporting wheels ; a valuable 

 object-lesson for the pupils of his Experimental Labora- 

 tory of Purdue University. The long-continued measure- 

 ment of the power, coal and water consumption, iS:c., of a 

 large engine in full work — for instance of a steamer, the 

 .l/tVfor and others — is one of the most interesting and 

 instructive that can be provided for a class of enthusiatic 

 students of mechanical engineering. G. 



Electric Light and Pou'cr. By Arthur F. Guy, 

 A.M.I.E.E. Pp. 346. (London : Biggs and Co., 1894.) 

 SiiME books, like the pedlar's razors, arc made to sell 

 rather than for use. Mr. Guy's volume is not one of 

 these. It has been issued " for the purpose of |)lacing 

 on record useful practical knowledge obtained by the 

 author during several years' experience of central-station 

 work, together with brief explanations of the laws which 

 govern the action of electrical apparatus in general use 

 for electric lighting." This brief description shows clearly 

 the ground covered. There are many similar works in 

 the market, but we do not know of one better suittd to 

 give the manipulator of electric dynamos an intelligent 

 knowledge of the forces with which he lias to deal. 



