DISCOVERY 



221 



activities the disturbance is attributed. But we have 

 seen that we may just as well start with the falling apple. 

 It has a flat frame of space and time into which pheno- 

 mena in its neighbourhood fit without distortion ; and 

 from its point of view bodies near it do not undergo 

 any acceleration. But when it extends this frame 

 farther afield, the simplicity is lost ; and it, too, has to 

 postulate the demon force of gravitation existing in 

 distant parts, and for example causing undisturbed 

 objects at the centre of the earth to fall towards it. 

 As we change from one observer to another — ^from one 

 flat space-time to another — so we have to change the 

 region of activity of this demon. Is not the solution 

 apparent ? The demon is simply the complication which 

 arises when we force the world into a flat Euclidean 

 space time frame into which it does not fit without 

 distortion. It does not fit the frame, because it is not a 

 Euclidean or flat world. Admit a curvature of the world 

 and the mysterious disturbance disappears. Einstein 

 has exorcised the demon. 



SCIENTIFIC BOOKS 



hiorganic Chemistry. By T. Martin Lowry, D.Sc, 

 F.R.S. (MacmiUan & Co., 28s.) 



This is an excellent book, undeniably the best of its kind 

 in Enghsh. The worst that one may say about it is of 

 its cost, which is distressingly expensive. But its pur- 

 chase is worth while. It covers the ground of inorganic 

 chemistry which lies between that traversed by the 

 elementary books hke Alexander Smith and the larger 

 treatises like Roscoe. For the first time in a general text- 

 book we have the newer subjects such as atomic number, 

 isotopes, crystal structure, and Langmuir's theory of 

 valency not only explained but given their proper place 

 in the scheme. Very wisely Dr. Lowry has obtained 

 the assistance of specialists in several subjects in which 

 he does not profess a first-hand knowledge : in the 

 sections on isotopes, on pigments, on photography, on 

 glass, and in the chapter on radio-activity. So that, 

 although the field covered is broad, there is a sureness of 

 touch nearly everywhere which the conscientious com- 

 piler ^^•ith his S3-stem of card -indexes has never attained. 



A happy feature of this book is the important place 

 given to metals and their alloys. The average text- 

 book of chemistry stresses the non-metals too much, 

 and one of the reasons why students do not hke chemistry 

 at first is because they are tired of hearing about hydrogen 

 and ozone. Dr. Lowry gives the metals their due. 

 He deals with them from the physical-chemical stand- 

 point. Another obviously good feature is the excellence 

 of the diagrams, especially the beautiful photographs of 

 cr\-stals which have been well chosen and well reproduced. 



This book is recommended to the serious student w-ho 

 wants an informed and comprehensive account of the 

 whole subject in one volume, something more than that 

 contained in the elementary books studied at school or 

 in the first two years at coUege, and less than that in 

 the larger treatises or monographs. It is nevertheless a 

 book for the general reader also. Some textbook writers 



forget their readers and write to placate imagined critics. 

 This book is written for its readers ; a fact evident not 

 only in the pains the author has taken to ha\'e his informa- 

 tion accurate and up-to-date, but in the clear and con- 

 cise manner in which it is set forth. 



The A B C of Wireless. A Popular Explanation. By 

 Percy W. Harris. (The Wireless Press, 6d.) 



A plain straightforward attempt by the editor of 

 Conquest to tell the man in the street the elements of 

 wireless. Well written and printed, with a few excellent 

 photographs . 



Within the Atom. A popular view of Electrons and 

 Quanta. By John Mills. (George Routledge and 

 Sons, 6s.) 



The author knows what he is -writing about, but is 

 mistaken in believing he is appeahng to the general 

 reader. He tells us he wishes to make himself under- 

 stood by those " who have no previous knowledge of 

 electricity, mechanics, or chemistry," and then proceeds 

 to pour out such a vast store of information of a highly 

 technical kind that one would need to have an F.R.S. 

 at one's elbow as one reads. What he does do is to 

 describe briefly and, in the main, accurately the latest 

 work on the structure of the atom and related problems. 

 But only those who have already studied these matters 

 in the usual te.xtbooks will appreciate what he is describ- 

 ing. We think it is doubtful if such a complicated thing 

 as the inside of an atom can be explained in popular terms. 

 A writer would require to be exceedingly clever to write 

 such a description ; it would be an unselfish piece of 

 work. And one thing the writer must do is to consider 

 his intended readers, and not simply, conscioush^ or 

 unconsciously, as so many do, write to please liimself 

 or to keep himself in the good estimation of liis friends. 

 Tills, we tliink, is what Mr. ^liUs has done. And so he 

 has fallen between two stools ; for the weaker brethren 

 can digest httle of this book and the strong will like 

 their meat fresher. 



Life and the Laws of Thermodynamics. By Sir W. M. 

 Bayliss, -M.A., D.Sc, F.R.S. (H. Milford. is.) 



Sir William Bayliss' " Boyle Lecture " to the Junior 

 Scientific Club of Oxford University is hardly up to 

 the usual level of these lectures. It is evident that the 

 lecturer has been pressed to avoid .technicahties and to 

 keep simple, and we think he has taken the injunctions 

 to heart too literally. A. S. R. 



Man the Animal. By W. M. Smallwood, Ph.D. (New 

 York: The MacmiUan Company, 12s.) 



One of the most difficult tasks of the man of science 

 is to write a good popular book on his subject. The 

 present volume is a gallant attempt. It contains some 

 admirable photographs, bringing home very vividly the 

 early steps in embryology, and the appearance of cells 

 and tissues under the microscope, and treats of a variety 

 of interesting topics. It has two ambitious chapters on 

 methods of learning in man and animals. But it is some- 

 what too didactic, and often \3.ys, down natural " laws " 



