242 



NA TURE 



{July 12, 



speaking of the graphical characteristic of a dynamo, 

 language is used which would lead the reader to infer 

 that this important method in the theory and practice 

 of electrical engineering was introduced by M. Marcel 

 Deprez, the fact being that it was first introduced, fully 

 explained, and actually used by Dr. Hopkinson in 1879. ' 

 What M. Deprez did, was, we believe, simply to give a 

 name to Hopkinson's curve, and to further develop its 

 applications. It would be easy to correct, in footnotes 

 or otherwise, these and a few similar small blots on a 

 work which is, in most respects, remarkably fair and 

 cosmopolitan in its history. 



Regarding the work of the translator, we can, on the 

 whole, speak very favourably. There are, however, pas- 

 sages here and there which are so inadequately translated 

 that they suggest the idea of an inferior assistant not 

 always sufficiently overlooked. Compare, for example, 

 the following piece of the original with the accompanying 

 translation : — 



" Si la loi e'tait generale, on en conclurait, pour le cas 

 de deux plateaux paralleles, que la production de l'etin- 

 celle correspond toujours a unememe valeur de la densite 

 electrique et, par suite, de la force electrique et de la 

 pression electrostatique, ou, dans les ide"es de Maxwell, 

 a un meme e"tat ou une meme energie spdcifique du 

 milieu interpose"." 



" If the law was general, we should conclude, for the 

 case of two parallel plates, that the production of elec- 

 tricity almost represents the same value of the electrical 

 density, and therefore of the electrical force and the 

 electrostatic pressure, or, as in Maxwell's views, to the 

 same condition or the same specific energy of the 

 interposed medium." 



It will be seen that the English passage is not a trans- 

 lation of the French, is not English, and means nothing. 

 We mention this, by far the worst, case of loose trans- 

 lation that we have noticed, to draw the attention of the 

 English editor to the need there is for revision. Such 

 corrections as are absolutely necessary might be given 

 on a fly-leaf ; and, in order to help, we mention a few 

 things that we have noticed. Some are misprints, some 

 wrong, some merely doubtful. 



P- 39) "compass of horizontal intensity" ? 



P. 41, " observations " (oscillations ?) 



P. 48, "collate" (collect?) 



P. 50, " bodies of easy construction " ? 



P. 237, "combine the experiment"? 



P. 293, " but they are not sufficiently so, &c. " ? 



P- 557) " residues of the Leyden jar" ? 



P- 577) " induced charges" (decharges induites) ? 



P. 578, " to make the co?tstant of the ballastic galvano- 

 meter " (faire la tare : why use tare ? Tare is English). 



P. 878, "regulation of a galvanometer" (tarage d'un 

 galvanometre) ? 



Notwithstanding minor shortcomings, this English 

 translation of the work of MM. Mascart and Joubert 

 will be of great use to English readers ; and we hope 

 that it will not be thought that, by calling attention to 

 inaccuracies here and there, we mean to depreciate the 

 labour of the editor, or to undervalue the debt which the 

 English scientific public owes him for rendering more 

 accessible one of the most important electrical treatises 

 of the day. G. C. 



1 See his papers in the Poceefngs of the Institution o." Mechanical 

 Engineers, April 1879 anJ Ap.il iS^o. 



SYNOPTICAL FLORA OF NORTH AMERICA. 

 Synoptical Flora of North America : the Gamopetalar. 

 A Second Edition of Vol. I. Part 2, and Vol. II. Part 1, 

 collected. By Asa Gray, LL.D. Large 8vo. 480 4* 

 494 pp. (Washington : Published by the Smithsonian 

 Institution, 1888.) 

 ' I 'HE first feeling which the sight of this book re- 

 *■ awakens in the mind is one of deep regret that 

 Prof. Asa Gray did not live to carry out the plans he 

 had entertained so long for an elaboration of a complete 

 flora of Temperate North America upon one uniform plan. 

 A work of this scope was planned by Dr. Torrey and 

 himself when he was quite a young man, and the first part 

 appeared as long ago as 1838. It was soon found by the 

 anthers that it was impossible to identify satisfactorily the 

 plants which had been named by their predecessors 

 without studying the European Herbaria; and in order to 

 do this Dr. Gray spent a year in Europe in 1838-39. 

 Another instalment, which extended to the end of Poly- 

 petalse, was published in 1840, and the remainder of the 

 first volume, extending to the end of Composite, in 1842. 

 Then Dr. Gray accepted the post of Fisher Professor of 

 Natural History in the University of Harvard, and what 

 with teaching and herbarium work, and the preparation 

 of the successive five editions of his " Flora of the 

 Northern United States," and the elaboration of the new 

 collections that poured in as fresh territories were ex- 

 plored and settled, his time was fully occupied for 

 thirty-five years. In 1878 he returned to the more 

 comprehensive work, and in that year published the 

 first part of the second volume, which includes the re- 

 maining orders of Gamopetalae, from Goodeniaceae to 

 Plantaginaceae. In 1884 he issued a revised edition of 

 the part devoted to the Composite and small allied 

 orders. The work we have now before us is a re- 

 print of the whole of the Gamopetalae, with two sup- 

 plements, embodying additions and corrections up to the 

 end of 1885. Although the title-page bears the date of 

 1888, it was really issued, as the secondary title-page 

 indicates, in January 1886, and we have had it in use at 

 Kew for a couple of years. The present volume, there- 

 fore, covers the central third, brought up to date, of the 

 complete undertaking as planned ; and at the beginning 

 the Polypetalous Dicotyledons are still left as they stood 

 in 1840, except for the most useful bibliographical index, 

 brought up to date, which Dr. Sereno Watson issued in 

 1878; and the Incompletae and Monocotyledons, to 

 which Dr. Watson has happily devoted special attention 

 during many years, have still to be dealt with. 



The flora of Temperate North America contains 

 about the same number of species as that of the whole of 

 Europe, but of course the orders are to a certain extent 

 different, and others enter in the two floras in very 

 different proportions. In the present work there are 

 described 3521 species of Gamopetalous Dicotyledons, of 

 which all but 162 are indigenous. They fall under 562 

 genera, of which 520 are native. The American Com- 

 positae alone, 1636 species, far more than outnumber tl 

 whole Phanerogamic flora of Britain. Next to'^Cor 

 positse come Scrophulariaceae, represented by 367 sp 

 cies and 38 genera. Of Hydrophyllaceae, an order near 

 restricted to North America, there are 129 species 

 14 genera ; of Polemoniaceae, another nearly' endemi 



