November 8, 1900] 



NATURE 



27 



described and explained. The third chapter is occupied 

 with the frequency and pitch of notes, methods of deter- 

 mining the period of a tuning fork, Doppler's piinciple 

 and musical scales. Whilst comprising little that is new, 

 the account given should prove very useful to students. 

 A short account of resonance and forced vibrations is 

 given in the fourth chapter, whilst the succeeding chapter 

 is occupied with the analysis of vibrations. The mathe- 

 matical investigation on p. 66, concerning the super- 

 position of harmonic curves, might advantageously have 

 been given rather more in detail considering the class of 

 students for whom the book is written ; but there are few 

 other instances where this objection can be raised. 



Chapter vi. is concerned with the vibrations of strings, 

 and a very useful and systematic account of this part of 

 the subject is given. This should prove very acceptable 

 to students as leaving unexplained no point on which 

 difficulties are likely to hang. The vibrations of air in 

 pipes, and of rods, plates and membranes, are treated of 

 in an equally satisfactory manner in Chapters vii. 

 and viii. 



One of the most interesting chapters in this volume is 

 the ninth, devoted to singing flames, sensitive flames and 

 jets, and musical sand. Lord Rayleigh's investigation of 

 the conditions necessary for the production of a singing 

 flame is clearly and simply explained, and many other 

 phenomena dependent on similar principles are described. 

 The description and explanation of the musical note, 

 produced when certain sands are struck or otherwise 

 disturbed, will doubtless be read with great interest. 



Finally, it may be confidently predicted that this volume 

 will meet with an appreciative reception from all serious 

 students of physics. It is characterised throughout by 

 the absence of obscure and inconclusive reasoning such 

 as is sometimes found in treatises dealing with intricate 

 problems in an elementary manner, by the employment 

 of sound yet simple mathematical methods, and by the 

 inclusion of accounts of recent work not to be found in 

 other books of the same class. Many students might 

 wish that examination questions had been added at the 

 end of each chapter, and some may consider that sixty- 

 six pages of advertisements at the end of the book some- 

 what exceed what might have been expected in this 

 direction. Otherwise it would be difficult to find grounds 

 for any sentiment but gratification that a gap in our 

 scientific literature has been so worthily filled. 



E. E. 



GEOLOGY AND PRACTICE. 



Sieinbruchindustrie und Steinbruchgeologie : technische 

 Geologie nebst prakiischen Winkenfiir die Verwertung 

 von Gesleinen^ unter eingehender Beriicksichtigung der 

 Steinindustrie des Konigreiches Sachsen. By Dr. O. 

 Herrmann. Pp. xvi -f 428. (Berlin : Borntraeger, 1899.) 



IN its elaborate title, of which we have omitted the 

 concluding lines, this work explains its own exist- 

 ence. While it gives a useful account of methods of 

 quarrying, and of the practical applications of various 

 kinds of stone, it specially describes the rocks of Saxony 

 and their economic relations at the present day. The 

 two divisions, general and special, occupy almost equal 

 space, and it will be seen that the book is thus a valuable 

 addition to our libraries. What some of the American 



NO. 1619, VOL. 63] 



.States have done for their own areas, what Mr. G. H. 

 Kinahan did for Ireland, in his papers on " Economic 

 Geology," is here repeated for a country of great 

 geological interest. It appears that in Saxony, as in 

 London itself, the use of stone for buildings of a 

 permanent character is becoming more and more exten- 

 sive, while increasing demands are made upon the 

 quarries for ordinary engineering works. 



Dr. Herrmann prefaces his book by an account of the 

 more common rock-forming minerals, and of the rocks 

 ordinarily quarried. This is said to be "zur Orientierung 

 fiir Nicht-Geologen" ; but naturally the elements of 

 mineralogical knowledge are presupposed. A quarry- 

 owner would not be expected to identify his minerals from 

 the descriptions given here, but would doubtless have re- 

 ceived, in his preliminary scientific training, a good 

 foundation of chemistry and some practical acquaintance 

 with the materials of the earth's crust. Dr. Herrmann 

 therefore does well to emphasise, in his descriptions, the 

 characters that give each mineral or rock its importance 

 from a technical point of view. The lists of locaUties, 

 reminding one of those in Roth's "Allgemeine Geologic," 

 and references to the buildings where certain rocks have 

 been employed, might, it seems, have been omitted from 

 this section, in view of the forty-three pages devoted to 

 this subject in a later portion of the work. 



The author, writing as recently as 1899 (p. 53), places 

 all the ordinary lavas, rhyolite, basalt, and so forth, as 

 " Eruptivgesteine tertiaren und nachtertiaren Alters," a 

 classification which is merely playing with words, and 

 which has only a superficial justification in the field. His 

 excuse must lie in the powerful continental combination 

 in favour of an arrangement which, to Western minds, 

 savoured too strongly of the Wernerian school ; its 

 abandonment of late years may, indeed, mark the 

 breaking down of the " mineral cabinet " system of 

 geology, which the spread of microscopic research 

 tended at one time to maintain. 



The valuable section of the work (pp. 123-18 1) on the 

 characters required in rocks selected for various industrial 

 purposes, and on methods of extraction, is illustrated by 

 photographs of actual quarries, taken by the author. We 

 then pass to the special consideration of the application 

 (Verwertung) of the rocks of Saxony to the technical 

 requirements of the country. Many of these rocks are 

 so well known to every student of geology that an 

 account of their mode of occurrence, from a new point of 

 view, is of scientific as well as industrial importance. 

 We notice the tendency to introduce foreign stones side 

 by side with those of some well-worked local quarry, the 

 materials being cut and polished on the same spot. 

 The natural demand for variety in the colour-scheme o* 

 our great city-buildings will often limit the demand for a 

 local stone, however excellent, and " foreign competition '* 

 may be favoured by good taste as much as by a war of 

 prices. 



The account of the Serpentine of Zoblitz, which " has 

 arisen from the alteration of a Lherzolite," is a good 

 example of the interest attaching to the author's mode of 

 treatment. His historical review extends back to the 

 cutting of the stone by a herd-boy, as he watched his 

 cattle, in the middle of the fifteenth century (p. 255). 



As an illustration of the many details of geological 



