August 29, 1907] 



NA TURJi 



4+3 



apparatus consistine;- of thin plate orifices, large con- 

 necting boxes and delicately poised vanes, is figured 

 and described by which the fundamental pneumatic 

 laws mav be demonstrated. For example, if H be the 

 head or aeromotive force, R the resistance, or sum 

 of resistances, and V the volume of air delivered, using 

 comparable units, the relation H = RV^, corresponding 

 with Ohm's law E-RC, is shown to exist. 



The book is divided into three chapters comprising 

 respectively 26, 19, and 33 pages. The first deals with 

 the laws of flow in air circuits and their verification, 

 in the manner already referred to. The second with 

 the physical principles applicable to the ventilated 

 space, in which the important effects of changes of 

 temperature and the convection currents resulting 

 therefrom are discussed, and some sketches of delicate 

 and simple apparatus used by the author in his inves- 

 tigations, together with some real and ideal thermal 

 diagrams, are given. In the third chapter are dis- 

 cussed the essentials for practical ventilation, and, so 

 far as the limits of the book permit, the various sys- 

 tems in general use. Here attain the electrical 

 analogy is given full play, and applied to the consi- 

 deration of the open fire, the cowl, the vacuum and 

 plenum systems, and to simple cross-ventilation. 



The diction throughout the book is so clear and 

 concise that we cannot even quarrel with Dr. Shaw 

 when he refers to a draught along the floor as likely 

 to set up " the reversed correlative of the therapeutic 

 action " of putting one's feet in water, and we heartily 

 endorse his suggestion that this important subject 

 should receive more attention at the hands of those 

 engaged in scientific research in our technical insti- 

 tutions. 



OVR BOOK SHELF. 

 The Aim and Achievements of Scientific Method: an 



Epiitemological Essay. By Dr. T. Percy Nunn. 



Pp. X + 144. (London: Macmillan and Co., Ltd., 



i(|07) Price 3X. 6d. net. 

 Tills essay is an expansion of a paper read before 

 the Aristotelian Society in February, 1906, and was 

 in its present form printed in September, 1906, and 

 presented to the University of London as a thesis for 

 the degree of Doctor of Science. The results de- 

 scribed were reached in the course of a study of the 

 problems of science teaching in schools, but its 

 pedagogical applications are not considered in the 

 present volume. 



The essence of the doctrine presented by the author 

 is the view that a large part of the contents of our 

 consciousness from moment to moment consists of 

 elements which exhibit themselves as having a certain 

 unique " priority " to our conscious processes. These 

 elements constitute what he describes as the objective. 

 The aim of the scientific process is to render objective 

 facts intelligible to an individual consciousness by 

 building up the primary facts into " secondary con- 

 structions " by means of ideas drawn from other con- 

 texts of experience. No hypothesis is considered 

 essentially incapable of making primary facts intel- 

 ligible on the ground of the context of experience 

 from which it is drawn, while the hypothesis is in no 

 case to replace (in the sense of accounting for the 

 " reality " of) the objective facts which it has been 

 employi-d to render intelligible. The extent to which 

 unification of the various provinces of scientific inquiry 



NO. 1974, VOL. 76] 



can be brought about is idcnlic.il with the range over 

 which hypotheses drawn from a single context of 

 experience can be applied to illustrate facts. 



The author examines briefly the most systematic 

 of the attempts that have been made to render the 

 whole range of sensible facts intelligible by means of 

 the concepts of "mass" and "motion," which are 

 themselves drawn only from one province of primary 

 facts. Iluygens, in his discussion of the collision of 

 elastic bodies, made use of wliat Mach calls an " in- 

 stinctive perception," that the centre of gravity of a 

 system left to itself cannot rise; this was by the Ber- 

 noullis developed into the principle of vis viva, upon 

 which Helmholtz based his wider principle of the 

 conservation of energy, which first brought the facts 

 of heat into a line with those of inechanics. But 

 though temperature changes are thus connected with 

 mechanical facts, the doctrine does not effect a reduc- 

 tion of the former to the latter, nor is Lord Kelvin's 

 absolute thermodynamic scale more successful, as it 

 makes no attempt to deduce from dynamical data the 

 experiences to which the notion of temperature refers. 

 Kven the theory of Helmholtz is only partially suc- 

 cessful. The modern science of energetics expressly 

 declines to attempt to explain one set of objective 

 phenomena in terms of another, contenting itself with 

 trying to bring physical facts Into a form of unity 

 without reducing them to one type. In doing so it 

 exhibits a practice that accords with the philosophical 

 tenets of Dr. Nunn's essay. The hypothesis has, as 

 he shows, merely a transient function, to point the 

 way to new facts, including relations between things, 

 and should then efface itself. 



The Principles and Practice of Brewing. By Dr. 

 Walter J. Sykes. Third edition, revised by the 

 author and Arthur R. Ling. Pp. xviii + 588; illus- 

 trated. (London : C. Griflin and Co., Ltd., 1907.) 

 Price 2 IS. net. 

 The publication of a new edition of this well-known 

 book, which has been thoroughly revised by its 

 author, the late Dr. Sykes, in conjunction with Mr. 

 Ling, and brought well up to date, should be welcomed 

 by all interested in the scientific aspect of the brewing 

 industrv. In one respect we think the late author 

 and his colleague have lost an opportunity in not 

 revising the original plan of the book, together with 

 the matter it contains, for we have always considered 

 that the book suffered to some extent in usefulness 

 from the manner in which it was arranged ; but, how- 

 ever this may be, the work in it*; present form stands 

 easily first among books in our language devoted to a 

 consideration of the complex scientific problems under- 

 lying the brewer's art. 



The present edition, like the previous ones, is essen- 

 tially a treatise on the scientific nrincioles which 

 underlie brewing technology, and although the word 

 " practice " is included in its title, the space actually 

 devoted to a description of the various processes of 

 brewing and malting is comparatively small. In a 

 book which deals in a somewhat encyclopaedic manner 

 with many different branches of science, naturally 

 some unevenness is noticeable in the treatment of the 

 various subjects included, but none of the more recent 

 investigations of importance which bear on the subjects 

 discussed appears to have been overlooked, and the 

 references which are given add much 10 the value of 

 the book. The strongest part of the book is un- . 

 doubtedly the one which deals with the chemistry of 

 the carbohydrates, more especial!)- the chemistry of 

 starch, and the author's risumi of the investigations 

 which have been made in this country and abroad in 

 connection with the transformation of starch by 

 diastase is the most complete account of the subject 



