478 



NATURE 



[September 15, 1904 



moved from the walls and floor of glaciers wherever 

 the planes of division lie at favourable angles. In this 

 way, medial moraines have a very real existence below 

 the surface of the glacier as well as upon it, since a 

 rocky island yields ice-scratched material over its 

 surfaces of contact with the ice that sweeps round it 

 on either side. " Such medial moraines (p. 194) 

 possess only ground-moraine material"; the word 

 " only," however, seems negatived by the following 

 sentence : — " their constituent debris is not limited to 

 the surface, but reaches right down to the base. In 

 consequence, the debris seen at the surface is not 

 constant in quantity as in the pure medial moraines, 

 but increases in proportion as the end of the glacier 

 is neared, in accordance with the progress of ablation." 



Internal moraines may similarly arise from projec- 

 tions in the firn-area ; the fragments are carried for- 

 ward as a wall within the ice. A little diagram on 

 p. 203 makes Finsterwalder's scheme of moraine- 

 structure clear, though it perhaps exaggerates the 

 filmy character of the ordinary ground-moraine. 



It has seemed to many geologists that the increasing 

 stress laid on the plasticity of ice, and the ease with 

 which it adapts itself to obstacles, make it all the more 

 necessary to look to frost and storm, and to the erosive 

 action of sub-glacial streams, as the agents by which 

 glaciated hollows are cut out. The passages (p. 361 

 el seq.) on cirques — no such Gallic word is really 

 admitted to this treatise — and the forms of Alpine 

 valleys will show how much room there is for differ- 

 ences of opinion on this point. We fancy that the 

 views put forward by Dr. Hess as to the simple " pene- 

 plain " character of the pre-Glacial Alpine slopes will 

 receive considerable criticism from those who have 

 described the successive movements along the 

 mountain-axis in Miocene and Pliocene times. The 

 grouping of the pre-Glacial river deposits of France 

 and Switzerland, as they are traced back into the hills, 

 should give us some idea of the depth of the valleys 

 before the ice spread down into them. The work of 

 rivers at the present day in rapidly destroying the 

 Glacial troughs, and in carving out ravines on ice- 

 worn walls, leads many of us to regard glaciers mainly 

 as moulders and preservers of the basins which they 

 temporarily fill. Dr. Hess, however, extends his sup- 

 port of the excavation-theory to the Scandinavian 

 fjords (p. 388), and it is well to realise that these views, 

 once widely prevalent, have not lost their hold upon 

 men who can measure and observe. 



Modern English writers may find their contentions 

 somewhat slightly dealt with, and their names 

 occasionally mis-spelt. Through a certain Teutonicism, 

 moreover, the glacial terms familiar to three-quarters 

 of the globe are omitted from the text and from the 

 index. Scarcely any German work mentions roches 

 moutonnees, made classical by De Saussure; but it 

 is hard to see nieves penitentcs admitted as a new- 

 comer. 



In conclusion, Dr. Hess has produced a book that 

 must find a place in every scientific library, both as 

 the work of an original observer and as a record of 

 the active progress of geological research. 



Grenville a. J. Cole. 



NO. 1820, VOL. 70] 



MATHEMATICS FOR SCHOOLS. 

 Practical Geometry for Beginners. By V. Le Neve 



Foster and F. W. Dobbs. Pp. ix + 96. (London : 



Macmillan and Co., Ltd., 1904.) Price 2s. 6d. 

 Elementary Algebra. Part i. Bv \V. M. Baker, 



M.A., and A. A. Bourne, M.A. Pp. viii + 2754-111. 



(London : George Bell and Sons, 1904.) Price 35. 

 ,4 New Trigonometry for Schools. Part i. Bv W. G. 



Borchardt, M.A., B.Sc, and the Rev. A. D. Perrott, 



M.A. Pp. vii 4- 237 4- XXXV. (London: George Bell 



and Sons, 1904.) Price 2S. 6d. 

 The Elements of Plane Trigonometry. By R. 



Lachlan, Sc.D., and W. C. Fletcher,' M.A. Pp. 



V-I-164. (London: Edward Arnold.) Price 25. 

 Preliminary Practical Mathematics. By S. G. 



Starling, B.Sc, A.R.C.Sc, and F. C. Clarke, B.Sc, 



A.R.C.Sc. Pp. viii+168. (London: Edward 



Arnold.) Price is. 6d. 

 Constructive Geometry. By John G. Kerr, LL.D. 



Pp. 122. (London: Blackie and Son, Ltd., 1904.) 



Price IS. 6d. ' 

 New School Arithmetic. Part i. By Charles Pendle- 



bury, M.A., F.R..A.S., assisted by F. E. Robinson, 



M.A. Pp. xv+2o64-xxi. (London: George Bell 



and Sons, 1904.) Price 2S. 6d. 



THE Practical Geometry by Messrs. Le Neve Foster 

 and Dobbs consists of a collection of more than 

 seven hundred examples, grouped in sets, each set 

 illustrating some fundamental geometrical principle, 

 the whole covering the subject-matter of Euclid, 

 Book i. There is little or no descriptive matter, but 

 the examples themselves are carefully selected and 

 arranged, so as to lead the pupil by easy steps from 

 experimental quantitative work, in which geometrical 

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 knowledge thus obtained. In part i. the examples 

 are entirely practical. In part ii. the work is partly 

 deductive, and this section is intended to supplement 

 the study of pure geometry, and especially to be used 

 in conjunction with Mr. Allcock's " Theoretical 

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 in which the student finds scope for the application 

 of the knowledge he has obtained. The book will be 

 found very useful in supplementing any elementary 

 text-book which is confined to the abstract reasoning 

 of pure geometry. 



A feature of the Algebra by Messrs. Baker and 

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 ated examples provided at short intervals, enabling 

 even the very backward student who works through 

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 paper in the graphing of algebraical functions, the 

 solution of equations, and in other ways, thus greatly 

 adding to the interest of the work, and giving a better 

 insight into the nature of the subject. This book is 

 the first instalment of a larger work, to be completed 

 in a second volume. It carries the subject up to the 



