August 26, 1922] 



NA TURE 



273 



the author of this book, while the project is still under 

 discussion in this country. The chair being established, 

 the need of a text-book has been immediately felt 

 and M. Gavrian has met the want by his excellent 

 book. 



The first point that strikes one is that the author 

 does not assume previous knowledge of the subject but 

 begins by a discussion of the conditions to be satisfied 

 and the materials which are available, but it is obvious 

 that he expects the student to have a working acquaint- 

 ance with chemistry, physics and elementary engineer- 

 ing. 



The consideration of the action of vehicles on the 

 road surface and vice versa is clear and concise ; it 

 deserves to be well considered by every one who is 

 interested in the road problem as there is much 

 confusion and .uncertainty on this aspect of the 

 problem. 



Another section worthy of every commendation is 

 the chapter devoted to definitions and nomenclature. 

 The application of the same or similar names to different 

 substances and compounds in England, France and 

 America has led and can only lead to misapprehensions 

 and failure to take advantage of experience gained in 

 other countries. It is gratifying to note that English 

 nomenclature meets with his approval, and until a 

 standard international nomenclature is established his 

 summary of the differences will be most valuable. 

 The second and third chapters are devoted to a descrip- 

 tion of the production and testing of tars, pitches and 

 other binding materials, the latter of which is probably 

 worthy of more careful attention than is always given 

 to it, since some failures have undoubtedly been due 

 to materials differing in composition and properties 

 from those employed successfully elsewhere. 



A discussion of the relative usefulness and suitability 

 of various rocks and slags in combination with different 

 binders would have been useful as a separate section, 

 while the binder used in Rocmac deserves more space 

 as it has advantages in certain situations probably not 

 possessed in the same degree by other materials. 



Considerable attention is given to the manner in 

 which pot holes are formed and the obscure phenomena 

 known as corrugation of road surfaces. No conclusion 

 is put forward with regard to the latter, but the need 

 for careful research is urged. It is probably not a 

 simple problem and will resist resolution for some time 

 as the related problem of the corrugation of steel 

 rails subjected to electric traction has done although 

 the conditions can be much more exactly determined in 

 the latter case. 



M. Gavrian has collected a considerable quantity of 

 data on the tractive effort required on different types 

 of road surface and for different types of tyres ; this 

 NO. 2756, VOL. I 10] 



is all to the good as the publication of authoritative 

 figures should do much to reconcile transport owners 

 to the high cost of modern roads by showing that there 

 is reduction in cost in another direction. The destruc- 

 tive effect of certain kinds of tyre is also well brought 

 out and may help towards their elimination if it brings 

 home to the vehicle owner that any slight advantage 

 he may gain individually has to be paid for eventually 

 in greater expenditure on the road itself. 



A standard English text-book of this type would be 

 of great assistance to the student not only of highway 

 engineering but of general engineering also, as the 

 subject is too often neglected. 



Radio-Communication. 



(1) Die drahtlose Telegraphic und Telephonic. Bear- 

 beitet von Dr. P. Lertes. (Wissenschaftliche 

 Forschungsberichte. Naturwissenschaftliche Reihe. 

 Herausgegeben von Dr. R. Ed. Liesegang. Band 

 IV.) Pp. xi + 152. (Dresden und Leipzig: T. 

 Steinkopff, 1922.) 4s. 



(2) Marine Wireless Pocket Book for the Practical 

 Operator and Student. By "W. H. Marchant. Pp. 

 vii + 180. (London : Sir I. Pitman and Sons, Ltd., 

 1922.) 6s-. net. 



(3) Continuous Wave Wireless Telegraphy : A Non- 

 Mathematical Introduction to the Subject of Wireless 

 Telegraphy from the Engineer's Point of View. By 

 B. E. G. Mittell. (Pitman's Technical Primer Series.) 

 Pp. xvi + 114. (London: Sir Isaac Pitman and 

 Sons, Ltd., 1922.) 2S. 6d. net. 



THE development of the art of radio-communication 

 has been so rapid that much of the apparatus 

 described in technical books on the subject is either 

 obsolete or is very little used. Its inclusion, however, 

 may be justified on the ground that it is wanted by 

 students for examinational purposes. As the number 

 of books on the subject is large and is rapidly increasing, 

 the expert who reads them all will naturally weary of 

 going over the same ground so often. 



(1) Dr. Lertes's book will be of value as a work of 

 reference. The descriptions are much too brief to be 

 followed by any one who is not thoroughly familiar 

 with the subject. A wealth of references are given 

 which will be useful to any one who is making a special 

 research on some branch of the subject. It would, 

 however, be a help to the reader if the references were 

 subdivided under various headings such as mathe- 

 matical, physical, technical, and commercial. The 

 °round covered is very wide and an account of the 

 Johnsen and Rahbek electrostatic relay is included. 



(2) This pocket book is intended principally for the 



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