December 14, 191 1] 



NATURE 



207 



soda process of Dyar and Hemming. The Leblanc 

 process lives mainly on account of the commercial 

 value of its by-products, but its continued existence 

 ( ven from this cause is seriously threatened by the 

 rapid extension of the methods of producing electro- 

 lytic chlorine. Dr. Lunge, no doubt, has it in con- 

 templation to complete his picture by the republica- 

 tion, revised and enlarged, of the third volume of 

 the former edition of his work, in which he dealt with 

 what was then publicly known of the methods of 

 cairying out the ammonia-soda process, as developed 

 by the Solvays, their coadjutors and successors. 

 The appearance of this volume will be awaited with 

 great interest. 



In its essential features this edition differs in no 

 material particular from its predecessors. The plan 

 of the original work is substantially unchanged. 

 Inuring a large portion of his long career as a tech- 

 nologist, Dr. Lunge was intimately associated with 

 tlie practical conduct of the Leblanc process — a pro- 

 cess which was nowhere more successfully worked 

 than in England, which constituted, indeed, the chief 

 of our chemical industries, and brought in the aggre- 

 gate great wealth to those concerned in it. The 

 quondam head of the chemical department of the 

 famous school of technology at Zurich long ago con- 

 stituted himself the historian of this time-honoured 

 process, which, whatever the future may have in 

 store for it, will always be accounted as one of the 

 most considerable and important of the manufactur- 

 ing methods of which chemical technology has any 

 record. It occasionally happens that threatened pro- 

 cesses, like threatened men, live long. We may 

 express the hope, then, that the days of the Leblanc 

 process are not numbered, and that Dr. Lunge may 

 still long be with us to note and chronicle the changes 

 which may come over it. 



GEOMETRY AND ALGEBRA. 

 (i) A New Geometry. By W. M. Baker and A. A. 

 Bourne. Pp. xxii + 246 + vi. (London: G. Bell and 

 Sons, Ltd., 191 1.) Price 2s. 6d. 



(2) Algebra. Part II., for the Use of Students pre- 

 paring for the Intermediate and Previous Examina- 

 tions of Indian Universities. By Prof. K. P. Chot- 

 toraj. Pp. iv + 486. (Simla, Calcutta: A. K. 

 Chottoraj, 1910.) Price 1.12 rupees. 



(3) Parametric Coefficients in the Differential 

 Geometry of Curves. By Dr. S. Mukhopadhyaya. 

 Pp. 31. (Calcutta: The University, 1910.) 



(0 '"PHIS text-book is an abbreviated and condensed 



J- form of the well-known work by the same 



authors published eight years ago, and therefore re- 



I quires little comment. The suggestion made in the 

 Board of Education circular on the teaching of 

 geometry that propositions should so far as possible 

 be taken in groups has been adopted. Thus theorems 

 on parallels form the first, properties of a single 

 triangle the second, tests for congruence the third, 

 and constructions the concluding section of book i. 

 The authors have throughout included considerably 

 iinore material than is required by (he Cambridge 

 NO. 2198, VOL. 88] 



schedule, particularly in reference to proportion and 

 areas. The last fifty pages of the book are devoted 

 to solid geometry. The properties of line and planes 

 are treated in a fashion very similar to Euclid XL; 

 this is followed by a number of properties of the 

 tetrahedron, pyramid, cylinder, cone, and sphere. An 

 excellent collection of examples on the mensuration 

 of solid figures is included. 



(2) The subject-matter of this volume ranges from 

 quadratic equations to the exponential and logarithmic 

 series, and in doing so covers more than four hundred 

 closely printed pages. It is therefore evident that the 

 treatment is very thorough. There is indeed far too 

 much detail ; all sorts of special and artificial cases 

 are dealt with, apparently in order to fortify the 

 student against every possible difficulty he may be 

 likely to encounter. For those whose sole object is 

 to pass examinations this may be advantageous, but 

 on general grounds it is highly undesirable. The 

 author has a lucid style, and has evidently arranged 

 both the text and the examples with the greatest care. 

 His book should be most useful to the teacher, but 

 we are inclined to think it will be rather oppressive 

 for the student. 



(3) This pamphlet is the result of a series of in- 

 vestigations the author has made in differential 

 geometry. The method of parametric coefficients was 

 evolved from an attempt to obtain by elementary 

 means expressions for the radius of curvature and 

 aberrancy in terms of the arc. The first part of the 

 paper deals with the properties of parametric co- 

 efficients of n-dimensions, and then applications are 

 made to plane curves ; these include the deduction 

 of the equation of the osculating cubic and the general 

 differential equation of the cubic. It is stated 

 that additional applications will be found in a 

 further paper by the author which will be published 

 shortly. 



MECHANICS AND TESTING OF MATERIALS. 



(i) Elements of Mechanics, with Numerous Examples 

 for the Use of Schools and Colleges. By G. W. 

 Parker. Pp. ix + 245. (London : Longmans, 

 Green, and Co., 191 1.) Price 45. 6d. 

 (2) A Handbook of Testing. By Prof. C. A. M. 

 Smith. Materials. Pp. xii + 284. (London : Con- 

 stable and Co., Ltd., 191 1.) Price 6s. net. 

 (i) TTHIS book is intended for the use of students 

 -1- having only a comparatively elementary 

 knowledge of mathematics ; great care has been taken 

 to ensure that the student should acquire thoroughly 

 clear ideas of the first principles which form the 

 groundwork of the subject, and this has been borne 

 in mind in working out the numerical examples illus- 

 trating the various laws. The first part of the book 

 is devoted to statics, the branch of the subject of 

 perhaps the greatest importance to the engineer ; com- 

 position and resolution of forces in one plane, 

 moments of forces, parallel forces, couples and their 

 composition, centres of gravity, and conditions of 

 equilibrium are successively dealt with, and then the 

 ripplir.'ition of the laws, wliiih have been deduced, to 



