July 30, 1903] 



NA TURE 



293 



Even more striking is the description of a mimosa which 

 grew near Memphis: — "orav 8e rt? a^r\Tak twv k\<ovi(ov 

 uxTTTip dcpavaifufifva to. (f)vWa avfxniTrTfiv (fiaaif, (ira fxtra 

 Tt,va xpovov dva^KtiaKardai 7rdXi«' Km OdWfiv." 



Here the difficulty arises with regard to the species 

 which is denoted, but special investigation by Dr. 

 Schweinfurth elicited the information that in the 

 vicinity there grows Mimosa asperata, a plant the 

 sensitivity of which is almost unknown to botanists. 

 Another graphic description is that of the banyan, 

 ffVKTj 'ivSiKv, with the allusion to the roots developed 

 from the branches, which are roots because they are 

 lighter in colour and leafless. But the book contains 

 many similar points of interest, and Dr. Bretzl has 

 furnished abundant proof of the accuracy of percep- 

 tion and faculty of discernment possessed by some of 

 the ancient Greeks. 



The sources of information are to be traced to the 

 memoirs of certain of Alexander's retinue. These 

 manuscripts, which were deposited in Babylon, have 

 unfortunately been lost; but they were apparently 

 available to Theophrastus, who has worked up the 

 material with truly remarkable intuition. Between 

 the writings of Theophrastus and those of other 

 authors, notably Pliny, Dr. Bretzl draws a sharp Hne 

 of distinction, the distinction, in fact, between the 

 original thinker and the annotator. 



Practical Plane and Solid Geometry for Elementary 



Students. By Joseph Harrison. Pp. xiii + 250. 



(London : Macmillan and Co., Ltd., 1903.) Price 



25. 6d. 

 This little book will be found very useful for the teach- 

 ing of the fundamental principles of geometry to 

 young students. The most important properties of 

 triangles and other plane figures are illustrated by 

 means of accurate drawing and numerical calcula- 

 tion, and thus appeal more readily to the understand- 

 ing and memory than if the beginner were made 

 acquainted with them by means of the severe and 

 tedious logic of Euclid. The great advantage of such 

 a book as this is that it prepares the mind of the 

 beginner for methods of accurate logical demonstra- 

 tion at a later stage in his studies. The very large 

 number of numerical exercises requiring calculation 

 and the use of instruments should suffice to give the 

 student a very firm knowledge of all the important 

 part of elementary geometry; and for this reason the 

 book can be confidently recommended to teachers. 



The first ten chapters are of this useful kind ; then 

 follow some chapters on the nature of vectors and 

 their addition, including some properties of uniplanar 

 forces acting on a particle the necessity for which 

 may, perhaps, be doubted. In these chapters we meet 

 with a little careless writing which, doubtless, will 

 be corrected in the next edition. Thus, the first 

 sentence (or what should be a sentence) on p. 118 re- 

 minds us of Mr. Skae's item in " The Jumping 

 Frog " : a verb is missing and no assertion is made. 

 The use of the expression " in tandem, or follow-my- 

 leader " to indicate cyclic order in the sides of a 

 triangle is of doubtful propriety ; but such trifles con- 

 stitute, of course, no serious objection. 



The notation I, for the magnitude and direction of 

 a vector (p. 130) is distinctly useful in the composition 

 of vectors. Chapter xiii., on concurrent forces, will, 

 of course, be omitted by the beginner whose aim is 

 to acquire only a knowledge of the elements of 

 geometry ; and it scarcely belongs to the subject. 



The remaining five chapters deal with geometrical 

 drawing in three dimensions, and they constitute a 

 very good introduction to the subject, the figures being 

 very numerous, and accompanied by a large number 

 of numerical examples. 



NO. 1 76 1, VOL. 68] 



Die Aluminium-Industrie. By Dr. F. Wintelen. 

 Pp. xi+io8. (Braunschweig: Friedrich Vieweg 

 and Sohn, 1903.) Price 6 marks. 



This very interesting monograph upon the aluminium 

 industry commences with a short historical introduc- 

 tion, in which we learn that Davy, so far back as 1808, 

 after he had discovered sodium and potassium, en- 

 deavoured to prepare aluminium by electrolysing, 

 alumina. In this he was not successful, and it fell 

 to the lot of Wohler in 1827 first to prepare the 

 metal by purely chemical methods. Bunsen, how- 

 ever, was able in 1854 to obtain it by electrolysing its 

 chloride. In a table on p. 5 the variation in the price 

 of the metal is traced since 1854, when it was merely 

 a chemical curiosity. Its value in that year was 120/. 

 per kilo, and even in 1889 it cost 2/. ; but with the 

 improvements of the electrical methods, the price 

 rapidly dropped, until in 190 1 it ranged from 25. to 

 25. 6d. per kilo. Following the historical portion of 

 the work, a very full account of the physical and 

 chemical properties of the metal is given. It is not 

 until we reach p. 22 that the present methods of 

 obtaining the metal are gone into, but here the 

 thoroughness of the treatment leaves nothing to be 

 desired. In the first place a careful account of the 

 preparation of the outgoing materials used in the 

 manufacture is given. This part of the work is of 

 very considerable value. Everyone is aware that 

 bauxite and cryolite are the substances used for pre- 

 paring aluminium, and those who have studied the 

 subject know that these substances cannot, as a rule,, 

 be employed without being first purified. In this 

 book the methods of purification are described in 

 detail, and methods of analysis are also set forth. 

 Page 54 is headed "carbon electrodes"; these are 

 employed both for the anode and kathode, in con- 

 sequence of impurities introduced into the bath when 

 other electrodes are used. The author gives details 

 of the manufacture of these carbon electrodes — ter» 

 pages are devoted to this. Some useful diagrams 

 illustrating the way in which the electrodes become 

 corroded during the electrolysis are also given. 



The last few pages of the monograph are devoted 

 to the " working up of the metal "; one of the most 

 interesting points being the method for welding the 

 metal which is employed by Heraus, of Hanau. It 

 consists in heating aluminium sheets with a hydrogen 

 flame to a temperature of about 400". The edges are 

 then pressed together, and after being worked for 

 some time with the hammer, they weld together in 

 such a manner that tubes made in this way can hardly 

 be distinguished from seamless ones. 



This monograph is one of the most interesting and 

 useful which we have had the pleasure of reading for 

 a long time. The facts are well arranged, and 

 although there are 108 pages devoted to the single 

 subject of the aluminium industry, we do not consider 

 that the work suffers from prolixity; we wish this 

 could be said of many German monographs which 

 have lately been published. F. M. P. 



Die Konstitution des Kamphers und seiner wichtigsten 

 Derivate. By Ossian Aschan. Pp. xi+117. 

 (Braunschweig : Friedrich Vieweg und Sohn, 1903.) 

 Price 3.50 marks. 

 The chemistry of camphor and its derivatives has 

 occupied the attention of chemists for many years, and 

 has now become so specialised that it is almost im- 

 possible for the ordinary chemist to keep up with the 

 immense amount of research published in the journals 

 devoted to chemistry. The monograph by Prof. 

 Aschan is accordingly very welcome, and will be found 

 useful not only by the non-camphor chemist, but also 



