246 



NATURE 



[August 24, 191 1 



remote enough from the pulse of France all round it. 

 The author, aided by well-chosen views, shows us 

 how the volcanic masses have controlled the higher 

 features of the landscapes, and how the Loire stream- 

 system has cut through the lava-flows, while, on the 

 side of the Allier, lavas of the same age have descended 

 into a pre-existing waterway (p. 326). Full justice 

 is done to the phonolitic mass ot the Mezenc, explored 

 by Faujas de Saint-Fond in the middle of the 

 eighteenth century (p. 294). We miss the name of 

 this great investigator from the bibliography on p. 

 14, although Scrope's work in 1827 is mentioned. 

 The users of this guide will become such good geolo- 

 gists that they will surely like to turn the pages of 

 Saint-Fond's admirable folio. It may be hoped that 

 M. Boule will send many lovers of unspoiled country to 

 the strange and broken slopes of the Cevennes. "J'ai 

 compose ce guide," he writes, "avec un rare plaisir." 

 He has transferred this pleasure to the reader. 



G. A. J. C. 



The Pronunciation of English by Foreigners : a Course 

 of Lectures to the Students of Norhatn Hall on the 

 Phvsiologv of Speech. By Dr. Geo. J. Burch, 

 F.R.S. Pp. x+110. (Oxford : Alden and Co., Ltd. ; 

 London: Simpkin, Marshall and Co., Ltd., 1911.) 

 Price 3s. net. 



This is a delightful book. Works on phonetics are 

 usually dry and uninteresting except to those who 

 are willing to face the technical difficulties of the sub- 

 ject. But Dr. Burch, who is well known in other 

 departments of science, invests the discussion with 

 both wit and humour, while, here and there, he gives 

 an amusing anecdote which is always appropriate and 

 telling. He deals with the difficulties experienced by 

 foreigners in catching the correct pronunciation of 

 some of the sounds of the English language. The 

 book is founded on lectures delivered at Norham Hall, 

 Oxford, to foreign women students, and during the 

 past ten years or so Dr. Burch has kept records of the 

 chief difficulties in the pronunciation of 1305 persons 

 of many different nationalities. He gives an excellent, 

 although a short, account of the general mechanism 

 of speech, and minutely describes the movements 

 necessary for the articulation of the speech sounds of 

 consonants, diphthongs, and vowels. There are also 

 excellent remarks on the breathing apparatus. 



It would seem that individuals of different nationali- 

 ties have different methods of using their nervous and 

 muscular mechanisms for articulate speech, so that 

 if one wishes to reproduce the sound in any given 

 language, one must learn how to train the articulating 

 mechanism so as to obtain the required result. Dr. 

 Burch gives minute directions, and it would seem that 

 his system of teaching the correct tones of English 

 to foreigners has had conspicuous success. 



"During these ten years I have been greatly struck 

 by the excellent pronunciation of the majority of those 

 attending these courses. If I could speak those 

 languages with which I am familiar with as good an 

 accent as mine is spoken by them, I should have every 

 reason to be proud. But this excellence has made a 

 severer critic of me." (P. 59. 1 



Excellent, however, as the description of the move- 

 ments of the tongue and other organs may be to 

 guide the student in reproducing a given sound, an 

 appeal to the ear is all-important, and those arc for- 

 tunate who have had the instruction communicated 

 by Dr. Burch's own living voice. We feel sure thai if 

 anyone lakes up this little book lie will not find it 

 dry and wearisome, as its title might indicate. It is 

 full of interesting information supplied bv one who is 

 an experienced and versatile teacher. 



John G. McKendrick. 

 V 1. 2lS2, VOL. 87I 



Praxis der Linsenoptik in einfachen Versuchen zur 

 Erldutcrung und Priifung optischer Instrument!!. 

 By Dr. W. Volkmann. Pp. vii+176. (Berlin: 

 Gebriider Borntraeger, 1910.J Price 3.50 marks. 

 This little book is one of a series composing a " Bib- 

 liothek fiir naturwissenschaftliche Praxis," in which 

 the object of each volume is to provide an introduction 

 to some branch of practical science by means of simple 

 experiments which can be carried out with inexpen- 

 sive and easily constructed apparatus. The optical 

 equipment here described consists of some half-dozen 

 lenses of different focal lengths, a number of simple 

 wooden stands, some clips and lens-carriers, 

 diaphragms, and screen, with a spirit lamp and strip 

 of gas-mantle to serve as light source. Even with 

 these simple means it is, of course, easy to arrange 

 an interesting and instructive series of experiments 

 to illustrate the properties of lenses and the formation 

 and defects of optical images. With a pinhole and 

 some fine gauze, one can go further, and study effects 

 due to the fact that light is a wave motion. With but 

 little increased expenditure the range of such experi- 

 ments could readily be extended ; but the apparatus 

 described is sufficient to enable practical acquaintance 

 to be made with nearly all the main defects of optical 

 instruments : spherical aberration, astigmatism, coma, 

 distortion, and chromatic aberration can all be 

 examined, and even the theory of resolving power can 

 be studied. The book concludes with chapters on the 

 photographic lens, the magnifying glass, the micro- 

 scope, and the telescope, in which application is made 

 of the experimental knowledge acquired to the 

 examination of the characteristics of a well-designed 

 optical instrument. 



To follow out the course of experiments here sug- 

 gested would no doubt be for an intelligent lad an 

 excellent introduction to the study of optics, and, 

 though the book is not designed for school use, the 

 German schoolmaster might find in it useful hints 

 in experimental science teaching. For the English 

 reader, however, it has no special interest; it shows 

 no exceptional ingenuity in the devising of experi- 

 ments, and, from its aim, novelty is not to be 

 expected, nor, perhaps, desired. 



Rhododendrons and Azaleas. Bv Wm. Watson. Pp. 

 xi+116. "Present-day Gardening" Series, edited 

 by R. Hooper Pearson. (London and Edinburgh : 

 T. C. and E. C. Jack, n.d.) Price is. 6d. net. 

 There are certain prevailing ideas with regard to the 

 constitution and requirements of rhododendrons which 

 are only partially correct that have tended to restrict 

 their cultivation. Thus the necessity for peat in the 

 soil is an exploded assumption, although the presence 

 of lime must be recognised as an effectual bar to 

 success. Then again the tenderness of many attrac- 

 tive species is only too obvious, but it is fortunately 

 possible to obtain hybrids of a more hardy character. 

 Further, it may be mentioned that no good popular 

 book on rhododendrons is extant; therefore the present 

 work is eminently desirable, and the publishers are 

 fortunate in securing the services of an author who is 

 an ardent enthusiast, and is also thoroughly con- 

 versant with the different classes of rhododendrons 

 and their special features. The classification in itself 

 is tolerably complex. Botanists recognise a single 

 genus which includes the true evergreen rhododen- 

 drons, a small group of Indian azaleas, also ever- 

 green- comprising l\. indicum and its allies — and 

 deciduous azaleas or swamp honeysuckles of North 

 America. The tun rhododendron species are best 

 developed in China, while Himalayan species, owing 

 their prominence to Sir Joseph Hooker, are a 

 favourite but tender group, and the North American 



