October 7, 1920] 



'NATURE 



^73 



foam-making- is not quite accurate. But this is 

 merely a crumpled rose-leaf. Summer's memories 

 deal with butterflies, British orchids, the behaviour 

 of a hunter-wasp, the ways of char, and the in- 

 surgence of climbing plants. Here also is in- 

 cluded an unashamed confession of faith in the 

 powers of the divining rod. In the fall of the 

 year Sir Herbert discourses on gossamer and 

 migration ; in midwinter he brings us up against 

 such problems as the otter's survival in the hard 

 months and the general question of animal intelli- 

 gence. In connection with animal behaviour, the 

 author inclines, if we understand him rightly, to 

 a somewhat remarkable transcendental conclusion, 

 that conscious intelligence is " the consequence of 

 an external and superior mandate or suggestion, 

 acting upon a suitable physical receptacle." 

 "Assuming a First Cause, instinctive activities in 

 the lower animals may be regarded as the com- 

 paratively simple and intelligible results of forces 

 initiated by him, acting- unerringly in prescribed 

 directions by means of co-ordinate organs modified 

 by evolution." In short, this lifelong^ student of 

 the ways of living creatures is frankly dualistic. 

 But he does not seek to ram his philosophy down 

 the reader's throat. 



VVe notice a few slips in the pages ; thus 

 Fabre's volumes are referred to as "Etudes Ento- 

 mologiques," and again as "Me^moires Entomo- 

 logiques," whereas the title was surely neither. 

 But such slips are trivial in a book of great attrac- 

 tiveness. It is full of interesting^ observations; it 

 expresses and arou.ses the inquiring- spirit. Its 

 happy style suggests that the writing of it must 

 have been a pleasure, and that is certainly true 

 of the reading. VVe wish there had been an index, 

 for the topics touched on are numerous. 



Principles of Aeronautics. 



Aeronautics: A Class Text. By Prof. E. B. 

 Wilson. Pp. vii-f 265. (Xew York : John Wiley 

 ;md Sons, Inc. ; London : Chapman and Hall, 

 Ltd., 1920.) Price 22s. net. 



THE work under notice differs considerably in 

 conception and treatment from that usually 

 associated with the title "aeronautics." It is very 

 clearly written, and will be particularly valuable 

 to advanced students of the subject for many 

 reasons. On the other hand, it will not appeal 

 strongly to the less advanced worker who delights 

 to regard himself as "practical," for he will find 

 only a "skeleton airplane " of the simplest type 

 as a basis for all the calculations made. The more 

 usual curves by which Iab<iratory results arc ex- 

 NO. 2658, VOL. 106] 



pressed are subordinated to analytical expressions. 

 The peculiar advantages of this point of view are 

 obvious in many places, notably in the treatment 

 of tbe fall of bodies through air. Without con- 

 taining such original matter as that of Bryan in 

 "Stability in Aviation," the new volume expresses 

 ideas more nearly those of Bryan than of any 

 other writer on the subject. 



The introduction to the book includes the ideas 

 underlying simple flight and the aerodynamics of 

 aerofoils, and the chapters of this section are 

 probably of little importance. It is with the 

 chapter on " Motion in Two Dimensions " that the 

 serious student of aeroplane motion will begin to 

 appreciate the book, for here are collected -with 

 concise proofs the fundamental theorems in 

 dynamics which are otherwise only to be found 

 by per.severance in the reading of such volumes 

 as Routh's "Rigid Dynamics." The principles 

 are carried step by step to the consideration of 

 stability, and are then illustrated by example. The 

 study of motion in three dimensions is committed 

 to a following- chapter, and starts from the ap- 

 parently simpler problems relative to fixed axes 

 and uses these as a basis for developing the 

 theorems for moving axes. The reasons for the 

 ultimate simplicity of the latter in relation to com- 

 plex motions are given, and the treatment is direct 

 and helpful. The last chapter in the section de- 

 voted to rigid dynamics applies the equations 

 developed to the stability of the aeroplane. The 

 stage reached is not further than that of English 

 workers, and is obviously dependent on the latter 

 for much of its inspiration ; but the chapters are 

 more complete and self-contained than any others 

 available at the moment. 



The rest of the book is devoted to "Fluid 

 Mechanics," and here are interposed chapters on 

 the simpler theories generally known as " hydrau- 

 lics " and the more complex and unfortunately 

 less applicable theorems of velocity potential, etc., 

 of hydrodynamics. The ninth chapter introduces 

 the fundamental laws of laminar motion, and 

 develops the formula for an adiabatic atmosphere. 

 Then follow the important Bernoulli's theorem 

 and the Rayleigh expansion, which indicates the 

 velocity at which air must be considered as a com- 

 pressible fluid so far as the effect on the resistance 

 of bodies moving- through it is concerned. From 

 Bernoulli's equation the laws for Pitot and Ven- 

 turi tubes are developed on standard lines. 

 Viscous fluids are dealt with in steady motion up 

 to the ciilculations relating to Foisseuille's famous 

 experiments, and a table of coeflicienls of viscosity 

 is given. 



The fundamental principles of dynamicjU simi- 



