122 



NA TURE 



[December 7, 1893 



The book is clearly printed and illustrated, but would 

 be improved if the numbers of the diagrams were given 

 and referred to in the text. Where more than one diagram 

 is found on the same page, it is not always evident to which 

 diagram the lettering refers. The phrase "addition of 

 interest " might also, with advantage, be changed to some 

 other, less suggestive of commercial arithmetic. These, 

 hu vvever, are small defects which can easily be corrected 

 in a t:ubsequent edition. The merit of the book is not in 

 wliat it teaches, but in how it teaches ; and not the least 

 valuable part of it will be found in the introductory 

 remarks addressed to the teachers. 



Philip Magnus. 



THE PYRENEES. 

 Les Pyrenees. Par Eugene Trutat. (Bibliotheque 

 Scientifique Contemporaine.) (Paris : J. B. Baillicre 

 et Fils, 1894.) 



IN this volume Dr. E. Trutat gives a sketch, as the 

 full title states, of the mountains, glaciers, mineral 

 springs, atmospheric phenomena, flora, fauna, and man 

 in the Pyrenees, illustrated by woodcuts and diagrams, to- 

 gether with two small maps. The mountains differ from 

 the Alps in their greater sirnplicity of structure, for they 

 form " the most perfect type of a regular chain." Like 

 the Alps, this consists of an axis of crystalline rocks, 

 granites, gneisses, and schists, flanked on both sides by 

 deposits comparatively unaltered. But there is one im- 

 portant difference : in the Alps, systems anterior to the 

 Carboniferous are only recognised in the extreme east ; 

 in the larger part of the chain, rocks of that or of a later 

 age rest on crystalline schists, which must be very 

 ancient. But in the Pyrenees schists truly crystalline 

 are succeeded by great stratified masses which have 

 been much less markedly changed. The most ancient 

 of these are assigned to the Cambrian, though as yet 

 fossils either have not been found, or are too ill-preserved 

 to afford any certain evidences of age. It seems, how- 

 ever, clear that they are older than the Silurian system, 

 for the different members of this can be identified in 

 several places by their characteristic fossils. The 

 Devonian system is well developed, and followed by 

 limestones (marine), conglomerates, and slaty rocks 

 of the Carboniferous period. The occurrence of Per- 

 mian rocks is considered by Dr. Trutat to be doubtful. 

 Trias, of the Lorraine type, is found, followed by re- 

 presentatives of the various systems in orderly succes- 

 sion up to the Neocomian. Between this and the Cre- 

 taceous is a break, then the sequence continues till 

 after the Nummulitic age. Then, as in the Alps, began 

 the great series of movement, of what the present chain 

 is the outcome. Masses of eruptive rock are con- 

 nected with these disturbances. The enormous beds 

 of conglomerate, called the Poiidingiies de Palassou, 

 which sometimes surpass looo metres in thickness, recall 

 the Alpine iiar^elfliihe. Strata partly marine, partly 

 freshwater, represent the Miocene and the Pliocene ; the 

 Quaternary deposits presenting a general resemblance to 

 those of the Alps. 



The glaciers of the Pyrenees at the present day are 

 comparatively small, the length of the largest not exceed- 

 NO. 1258, VOL. 49] 



ing about 4300 metres, while that of the Great Aletsch is- 

 32 kilometres, but their former extent, as in the Alps, was 

 much greater. They filled the valleys, and even de- 

 bouched on the lowland ; that of the valley of Ariege 

 must have been about 70 kilometres long. The glacial 

 deposits have been assigned to two epochs, and Dr. 

 Trutat claims for the earlier a considerable antiquity. In 

 the Arirge he states that they underlie Pliocene marls, 

 and near the plateau of Lannemezan pass under the Mio- 

 cene deposits of Sansan. The sections which he gives are 

 very rough, and further proofs of these statements, which 

 involve obvious difficulties, are likely to be demanded. 

 The Pyrenees owe their existence, as has been said, to 

 post-Nummulitic disturbances, but they also afford evi- 

 dence of great movements, both anterior to the Carboni- 

 ferous and after the Neocomian, the latter apparently 

 being less marked. Movements occurred after the great 

 post-Eocene elevation, but of much less importance than 

 they were in the Alps. The other topics, mentioned on 

 the title-page, receive due notice, and the volume will be 

 found useful, as it gives, in a concise and convenient 

 form, much information about one of the most important 

 mountain chains in Europe. T. G. B. 



OUR BOOK SHELF. 



Les Cotera?its Polyphases. Par J. Rodet et Busquet. 

 (Paris: Gauthier-Villars et Fils, 1893.) 



To those desirous of obtaining a general knowledge of 

 the principles used in the calculation of the efficiency and 

 of the dimensions of polyphase motors, &c., this book 

 will be of considerable use. In the first part, the 

 calculation of the dimensions of, and losses in, the 

 conductors conveying the currents are worked out 

 at some considerable length, numerical examples 

 being given. In the other sections the generation of 

 polyphase currents, motors with rotating fields, and 

 transformers are dealt with ; in each case the general 

 principles of the machines now in use being described, 

 though no account is given of the details of their con- 

 struction. There is also a short account of some of the 

 plants for the transmission of energy by polyphase cur- 

 rents which have been installed, with a table summaris- 

 ing the tests and measurements made during the Frank- 

 fort Exhibition. 



Solutiofis of the Examples in iJie Elements of Statics and 

 Dyftamics. By S. L. Loney, M.A. (Cambridge : 

 Camb. Univ. Press, 1893.) 



Mr. Loney is indebted to a friend for these solutions, and 

 also for the revision of the whole of the proof-sheets. We 

 have glanced through many of the examples, and they seem 

 to be fully and clearly worked out on the whole, very little 

 being taken for granted. Students who cannot depend 

 on the presence of a teacher, will find that with a judi- 

 cious use of this key much may be self-taught. 



LETTERS TO THE EDITOR. 



[ The Editor does not hold himself responsible for opinions ex- 

 pressed by his correspondents. Neither can he undertake 

 to retuj-n, or to correspond with the writers of, rejected 

 manuscripts intended for this or any other part t"/ NATURE. 

 No notice is taken of anonyfiiozts co>nfmtnications.'\ 



Sir Henry Howorth and " Geology in Nubibus."' 



Sir Henry Howorth, in his repiy to Dr. Wallace and 

 Mr. LaTouche, concerning the excavating power of ice, rernarks 

 that he is "speaking to every man of science, geologist or 



