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NA TURE 



[August 21, I ! 



instruction," under Art. 115 of the Code, unless it have 

 a proper supply of casts and models for drawing. 



II. As to classes under the Science and Art Depart- 

 ment, and grants by the Department : — (a) That school 

 boards have power to establish, conduct, and contribute 

 to the maintenance of classes for young persons and 

 adults (being artisans) under the Science and Art Depart- 

 ment. That, in localities having no school board, the 

 local authority have analogous powers. 



IV. Secondary and technical instruction : — (a) That 

 steps be taken to accelerate the application of ancient 

 endowments, under amended schemes, to secondary and 

 technical instruction. (J>) That provision be made by the 

 Charity Commissioners for the establishment, in suitable 

 localities, of schools or departments of schools in which 

 the study of natural science, drawing, mathematics, and 

 modern languages shall take the place of Latin and 

 Greek, (c) That local authorities be empowered, if they 

 think fit, to establish, maintain, and contribute to the 

 establishment and maintenance of secondary and tech- 

 nical (including agricultural) schools and colleges. 



V. Public libraries and museums : — (b) That museums 

 of art and science and technological collections be open 

 to the public on Sundays. 



COTTERILL'S "APPLIED MECHANICS" 

 Applied Mechanics : an Elementary General Introduction 

 to the Theory of Structures and Mac/lines. By lames 

 H. Cotterill, F.R.S. (London : Macmillan and Co., 

 1884.) 

 AMONG the many indications of the increasing in- 

 terest which technical education, in its widest 

 extent, now calls forth, one of the most conspicuous is 

 the production of manuals and text-books on the various 

 subjects with which it deals. Amongst these there is 

 none which is more important than Applied Mechanics, 

 and, at the same time, we may add that there is none 

 which has been more in need of a good elementary text- 

 book. The great works on the subject by Rankine and 

 Moseley are not adapted for elementary teaching, in- 

 volving mathematical processes beyond the power of a 

 beginner, and thus it has come to pass that a country 

 renowned for its engineering triumphs and for the excel- 

 lence of many treatises dealing with the practical appli- 

 cations of applied mechanics, has hitherto possessed no 

 book devoted to an exposition of its principles and suit- 

 able for educational purposes. Those persons, there- 

 fore, who are familiar with Prof. Cotterill's work on 

 the Steam-Engine will have looked forward with much 

 interest to the publication of his long-advertised book on 

 "Applied Mechanics." Its recent appearance we venture 

 to think has in no sense disappointed their expectation, 

 for it bears on every page evidence that its author has 

 not only studied and become intimately acquainted with 

 his subject, but that he possesses the rare faculty of 

 having learned by experience in teaching, the best way of 

 presenting a subject so as to diminish its difficulties and 

 make rough places smooth for the footsteps of the be- 

 ginner. By assuming a knowledge on the part of the 

 reader of the elements of theoretical mechanics he has 

 been enabled to devote the whole of this large volume to 

 the exposition of the more complicated science, in which 



the principles of the former are applied to the problems 

 of construction presented to the architect and the engineer. 

 The treatise is strictly elementary in its methods, the 

 mathematics used being, almost without exception, of the 

 simplest kind, and many results, which have usually been 

 obtained by complicated investigations, are here arrived 

 at by neat and elegant simple processes. The style of 

 reasoning adopted is also very successful, being neither 

 too diffuse, nor, on the other hand, so much compressed 

 as to puzzle and dishearten the beginner by gaps in the 

 reasoning which his mental capacity is not able to bridge. 

 This is particularly evident in the earlier parts of the 

 book. Towards the end, in the section on Hydraulics 

 and Pneumatics, we think that sufficient fulness of ex- 

 planation has hardly been furnished, in dealing with the 

 application of the principles of Energy, Momentum and 

 Moment of Momentum, to Fluids, and especially in the 

 case of Hydraulic Motors, to enable the student to grasp 

 the subject without a frequent reference to some of the 

 text-books which the author names. 



Another point of supreme importance in wdiich Prof. 

 Cotterill's treatment leaves nothing to be desired, is the 

 manner in which he has attained the aim he set before 

 himself of endeavouring " to distinguish as clearly as pos- 

 sible between those parts of the subject which are uni- 

 versally and necessarily true, and those parts which rest 

 on hypotheses more or less questionable." In Applied 

 Mechanics it frequently, we may say usually, happens 

 that, owing to various disturbing causes, exact investiga- 

 tions are either impossible to effect or useless from a 

 practical point of view when carried out, owing to the 

 complexity of the results, and we are therefore led either 

 to adopt results derived from experiments conducted 

 under the guidance of a roughly approximate theory or 

 obliged to rely on experiment alone and, in studying the 

 subject, it is of prime importance that the exact limitations 

 should be stated under which the formula- and rules given 

 can with certainty be applied. This exact knowledge is 

 necessary not only in the interests of science, but also in 

 many practical applications involving the security of life 

 or property. Many writers on this subject have slurred 

 over or insufficiently estimated the importance of an exact 

 statement of conditions and limitations, and consequently 

 we are glad to recognise and point out the thorough and 

 satisfactory way in which this has been attended to by 

 the author. 



The book is divided into five parts, of which the first is 

 devoted to " The Statics of Structures." In this section 

 there is not room in an elementary work for much new 

 matter, but we may point out as specially good the manner 

 in which the communication of stress from part to part of 

 a compound frame is traced out. The relation and inter- 

 dependence of the primary and secondary trusses of such 

 a structure is here indicated more clearly than in any 

 work with which we are acquainted. 



The principal peculiarity of the book consists in the 

 complete adoption of Reuleaux's Kinematic Analysis as 

 the basis of the description and treatment of machines, 

 both in their kinematic and kinetic aspects. In this 

 system a machine is regarded as consisting "of a number 

 of parts so connected together as to be capable of moving 

 relatively to one another in a way completely defined by 

 the nature of the machine. Each part forms an element 



