March 1 1 , I 880] 



NATURE 



44 1 



will continue in spite of all contradiction, and the absolute 

 fact that not a single example is known with certainty to 

 have occurred within the Arctic Circle. However, slight 

 flaws like these do not seriously compromise Capt. Moore, 

 who has certainly succeeded in condensing a greater 

 amount of really valuable information into a small space 

 than any other ornithological writer with whom we are 

 acquainted. 



LINKAGES 

 Linkages. By J. D. C. De Roos. Van Nostrand's 

 Science Series, No. 47. i8mo, 87 pp. (New York, 

 1879.) 



IT is not often that one is able to trace a pedi- 

 gree with such success as we have been able to 

 achieve in the case of this little book. It appears from 

 the title-page that it is reprinted in its present form 

 from Van Nostrand's Magazine, having been translated 

 from a series of articles by M. de Roos in the Revue 

 Universale ties Mines. The latter gentleman admits his 

 obligations for the major part of his work to a translation 

 which appeared in the Revue Seientifique of November 24, 

 1S74, of the well-known lecture delivered by Prof. Syl- 

 vester at the Royal Institution in the same year, which 

 was based on M. Peaucellier's discovery described in the 

 Nouvelles Annates of 1873, but contained a large amount 

 of original matter. For the residue, with one exception, 

 to which we shall presently return, M. de Roos appears 

 to be indebted to a paper by M. Liguine, which he 

 mentions without stating where it is to be found, and 

 which, together with a memoir by M. Saint Loup re- 

 ferred to by M. Liguine, is apparently regarded as all 

 that has been written on the subject since the publication 

 of Prof. Sylvester's lecture. M. Liguine's paper is to be 

 found in the Nouvelles Annates for 1875; it discusses 

 Prof. Sylvester's lecture, the "contra-parallelogram" of 

 Mr. Hart, the "kite" of Mr. Roberts, and one of Mr. 

 Kempe's earliest linkages. The description of these 

 discoveries of Mr. Hart and Mr. Roberts is stated by M. 

 Liguine to have been obtained from an article by Prof. 

 Sylvester in the Revue Seientifique in 1875, but no men- 

 tion is made of the source from which a knowledge of 

 Mr. Kempe's linkage is derived. There is, however, 

 internal evidence that it is M. Antoine Breguet who pub- 

 lished an article in the Revue Industrielle early in 1S75, 

 which discusses the discoveries of Messrs. Kempe and 

 Hart referred to, and states that the writer's information 

 is derived from their original articles in the Messenger of 

 Mathematics of November, 1874. 



It is not to be wondered at, after this, that the work 

 before us, though recently published, contains no infor- 

 mation of later date than 1874, a time when the theory of 

 linkages was in its infancy. Under such circumstances 

 it would have been more creditable to the editor of " Van 

 Nostrand's Science Series" if, to the statement in his 

 preface to M. de Roos's book that "the subject has not 

 even yet received the attention which is fully its due," he 

 had added the qualifying words, "though very much more 

 has been done than is contained in M. de Roos's work, 

 which is at the present time, from the rapid advance 

 which has been made during the past five years, some- 

 what antiquated." As a matter of fact, not the slightest 

 hint is conveyed, from the beginning of the work to the 



end, that it does other than represent the present state of 

 the science of linkages. 



The book bears no signs, as far as editor and translator 

 are concerned, of being only vol. i., but M. de Roos does 

 conclude with a promise in a "future note" to discuss 

 a "new element," of which a diagram is given, briefly 

 noticed (not described) in a paragraph containing a mis- 

 leading misprint of O A . A B for O A . O B, which in the 

 absence of the "future note "may make it difficult for 

 the reader to understand what the new element is. The 

 translator proposes to name it the " Element of De Roos,'' 

 "in honour of its inventor ;" an examination in the light 

 of the correction we have indicated will, however, show 

 that whatever claim to novelty might have been advanced 

 five years ago (though we feel somewhat doubtful whether 

 even then the "discovery" of a combination of half a 

 " Peaucellier" and half a "Hart" would have entitled 

 the discoverer to have his name affixed to it), at the 

 present time when more general linkages have been 

 discovered of which it is only a particular case, none 

 such could be sustained. 



The bulk of the volume consists of applications of the 

 Peaucellier inverter and Prof. Sylvester's modifications 

 to the description of curves, the extraction of roots, 

 &c. These, though decidedly interesting, would in many- 

 cases be superseded at the present time by less cumb 

 some methods. The pages are plentifully supplied with 

 diagrams, which are, however, occasionally marred by 

 the omission of links. This is particularly to be regretted 

 in the case of Fig. 48, which exhibits one mode of 

 practically applying Peaucellier's parallel-motion to a 

 beam-engine. It may not be uninteresting to note that 

 this method is the same as that employed by M. Peaucellier 

 in a model furnished by him to the Conservatoire des Arts 

 et Meuers in Paris. 



We cannot but regret that what appears to be a useful 

 science series should be marred by the introduction of a 

 work which, possibly through no fault of the author, must 

 by its antiquity mislead its readers as to what has been 

 and remains to be done on the interesting subject of 

 which it treats. 



OUR BOOK SHELF 

 The American Entomologist. New Series, No. 1. January, 

 1880. C. V. Riley, Editor; A. S. Fuller, Assistant 

 Editor. (New York : Max Jaegerhuber.) 

 We are glad to welcome an old friend in an old face, after 

 nine years' absence. The idea of this journal originated 

 from that lamented entomological genius the late B. D. 

 Walsh, in the form of the Practical Entomologist. This 

 developed into the American Entomologist, and to this 

 was subsequently added, as part of the title, and Botanist. 

 The American Entomologist is now resuscitated, under its 

 former editor, the energetic Prof. C. V. Riley, and bids 

 fair to be a success. Purely descriptive entomology evi- 

 dently finds little favour in the eyes of the editors, " de- 

 scriptive " papers being limited to one page in each 

 number, or if more extended, the cost is to be paid by 

 the author, and the space so occupied is to be supple- 

 mentary. Thus, the aims of the journal are almost 

 exclusively biological and economic. It is just possible 

 this idea may, at some future time, be slightly modified. 

 The editors crave that indulgence usually accorded to 

 first appearances, but, having no doubt fully in mind 

 the fact that one of them is an old stager, they have 

 produced a "first" number of a most varied and useful 



