470 



NATURE 



[February 9, 191 1 



to an account of the oscillations of the margin of the 

 Scandinavian ice, and the formation during a resting 

 epoch of massive terminal moraines. A block of 

 Miocene sediments with undisturbed bedding, includ- 

 ing brown coal, and 30 metres thick, has been found 

 at Georgenswalde, as a transported inclusion in the 

 boulder-clay (p. 150). Marine clays with Yoldia and 

 many other molluscs are regarded, in opposition to 

 recent views in Sweden, as older than the maximum 

 extension of the ice. These beds seem, indeed (p. 156), 

 to have been deformed by the pressure of the ice. 

 One great forward movement of the glacier- front, and 

 one retreat, broken by pauses and small oscillations, 

 are held (p. 159) to explain the phenomena in Ost- 

 preussen. During a pause, which Prof. Tornquist 

 explains by the sinking of the ice into yielding glacial 

 deposits in a great depression in the south-east of the 

 province (p. 175), the pre-Glacial marine sands and 

 the earlier ground-moraines are said to have been 

 pressed up as a ridge, just as the growth of the 

 dunes along the northern coast has pressed up modern 

 marine beds out of the sea {cf. p. 209). The 

 photographs give vitality and interest to a strange 

 monotonous country, which we well remember, as we 

 crossed it under grey September clouds. The view of 

 Neidenburg (p. 167) reminds us of the gravels washed 

 from the retreating ice, and of the last villages of 

 Prussian Poland, joined by tracks of trampled sand. 

 On this broad outwash plain, the white-capped Cos- 

 sack riders, night and day, keep the boundary between 

 east and west along the fenceless fields. 



Grenville a. J. Cole. 



OUR BOOK SHELF. 



Orchids. By James O'Brien. Pp. xii+114. (Lon- 

 don and Edinburgh : T. C. and E. C. Jack, n.d.) 

 Price IS. 6d. net. 

 In the preface to this little book it is observed that 

 householders in suburban districts who have but one 

 conservatory may, if they choose, keep it furnished 

 with orchids at a less expenditure of time and money 

 than is needed for the usual occupants of such 

 structures. Frankly, we doubt it. The same thing 

 has been written many a time before and 

 doubtless many a confiding householder has tried 

 to do it, but so far as we can judge the successes 

 are few and far between. The author of this work 

 has devoted his life mainly to the study and cultivation 

 of orchids, and, like most experts, is apt to take 

 for granted a knowledge of certain fundamental prin- 

 ciples which for himself require as little consideration 

 as breathing, but which are nevertheless absolutely 

 essential to success. It is over these that the average 

 suburban householder with no special training comes 

 to grief. No doubt it can be done, especially by 

 persons with abundant time on hand, and plenty of 

 enthusiasm ; but not by the ordinary City man who 

 has to leave his orchids — their shading and ventilation 

 ■ — to the tender mercies of the jobbing gardener or the 

 occasional attentions of a distracted housemaid from 

 ten to six, the most important part of the day in 

 orchid culture. 



But whilst we cannot support the optimistic views 

 as thus expressed by the author, we can strongly 

 recommend his book. It gives a condensed, but 

 wholly admirable, account of the history of orchid 

 cultivation, of the structure of orchid flowers, of the 

 principles of building orchid houses, and the best short 



NO. 2154, VOL. 85] 



account we have yet seen of how to cultivate these 

 plants. Many who have themselves spent years 

 amongst orchids will read the book with profit and 

 pleasure. It is well printed, and is illustrated by eight 

 coloured pictures made from plants grown in the 

 famous collection of Sir G. L. Holford, at Weston- 

 birt. They represent the acme of the orchid cultiva- 

 tor's art. 

 Practical Mathematics and Geometry. By E. L. 



Bates and F. Charlesworth. Pp. viii + 446. (Lon- 

 don : B. T. Batsford, 19 10.) Price 35. net. 

 This book has been written with the view of meeting 

 the recent addition to the Board of Education 

 examination syllabus, which unites arithmetic, alge^^ 

 bra, and practical drawing under the heading of " Pre- 

 liminary Practical Mathematics." In deciding the 

 question as to the best teacher for the combined 

 course the following points cannot be ignored. The 

 mathematical teacher as a rule cannot be entrusted 

 to teach draughtsmanship — one of the most important 

 lessons a young technical student has to learn, and 

 one whichj! if spoiled at the start, is rarely remedied 

 later. On the other hand, the engineering teacher is 

 apt to attempt to specialise in mathematics too earlv; 

 again, his time is generally fully occupied with hir 

 own special work. 



The book before us contains 4^6 pages crowded full 

 of matter presumably considered essential for a first^ 

 year's evening course. It includes mathematical work 

 up to quadratic and other equations, logarithms and 

 variation, and plane and solid geometrv up to the 

 projections of simple solids and their sections. There 

 is little attempt to coordinate the mathematical and 

 drawing work. 

 Introduction a la Metallographie Microscopique. By 



Prof. P. Goerens. Edition Fran^aise traduite pat 



Prof. A. Corvisy. Pp. 227. (Paris : A. Hermann 



et Fils, 191 1.) Price 10 francs. 

 The English translation from the German edition of 

 this work appeared more than two years ago, and was 

 reviewed in Nature, vol. Ixxviii (1908), p. 387. The 

 present book, however, is not identical with any pre- 

 vious issue. It is a careful revision by F. Robin, and 

 is in advance of its predecessors in several respects. 

 The arrangement is somewhat more logical, the de- 

 scription of the measurement of temperature by 

 thermocouples being followed at once by a section 

 devoted to the methods employed in studying the 

 microscopic structure of metals, and the remainder of 

 the book is occupied bv an account of the constitution 

 of alloys, illustrated 'by a very large number of 

 examples. The iron-carbon alloys are dealt with in 

 detail in a separate section. The most important 

 additions of new matter are descriptions of many 

 series of binary alloys, which have been studied during 

 the last three' or four years, and a large number of 

 beautiful reproductions of photomicrographs of the 

 structure of metals. 



Das Radium und die Farben. By Prof. Dr. C. 



Doelter. Pp. viii+i33. (Dresden: Theodor Stein- 



kopff, 1910.) Price 4 marks. 

 This is a useful summary of the very numerous 

 observations which have been made on the colour 

 phenomena produced in minerals by the neighbour- 

 hood of radio-active bodies. Although the facility 

 with which experiments can be made with radium 

 (at least bv the fortunate possessor of an adequate 

 specimen of that substance) have given a specia 

 prominence to observation made with it, it is well 

 known that analogous colorations are produced by 

 kathode and Rontgen rays, and by ultra-violet light. 

 These subjects are included in the book, which con- 

 tains a full bibliography. 



