March 26, 1908J 



NA TURE 



48: 



metrical methods, the sign convention being made 

 clear. The " power " of a lens is defined, and 

 attention is directed to the optician's mode of calling a 

 convex lens positive. "Dispersion," "the eye," and 

 " defects of vision " are very clearly treated. 



The first six chapters in the volume on " Sound " are 

 devoted to vibratory and wave motion, and the author 

 has succeeded in giving a very clear, and at the same 

 time elementary, exposition of these somewhat difficult 

 subjects for the beginner. 



The three volumes form a suitable introduction to 

 the study of physics. 



(2) This book is intended for use in schools where a 

 four years' course is given as outlined by the pre- 

 sent regulations of the Board of Education. The 

 book is divided into three parts. Part i, represents a 

 first term's work in geometry and physics ; part ii. a 

 second and third term's work in geometr)' ; part iii. a 

 second and third term's work in physics. The book 

 is a copious collection of examples and practical exer- 

 cises in illustration of the chief elementary geometrical 

 properties of the straight line, parallels, triangles, 

 iiuadrilaterals, polygons, and circles. The construc- 

 tion and use of scales, graphs, measurements of 

 length, area, volume, and density are also dealt with. 

 Xo instructions are given as to the method of using 

 the instruments employed in performing the various 

 exercises. These are left for the teacher to supply. 

 The book should prove extremely useful as a class- 

 book, the multiplicity and variety of the exercises 

 being a boon to any teacher for purposes either of 

 work in class, in the laborator)', or at home. 



(3) These are two elementary laboratory text-books 

 forming, as their titles imply, a second and third 

 vears' course in practical physics for schools. The 

 second year's manual deals chiefly with heat, and 

 contains descriptions of methods of performing up- 

 wards of seventy experiments, the subjects treated in- 

 cluding thermometry, measurement of coefficients of 

 expansion, calorimetry-, conduction, convection, radi- 

 ation, solution, distillation, and crystallisation. In 

 addition, questions and supplementary exercises are 

 given after many of the experiments. The book 

 strikes one as being hurriedly compiled, the diagrams 

 in verv few instances being referred to in the text. 

 .\gain, on p. 8i a wire i2in. long 3/32in. diameter 

 is to be bent 2 cm. from the end. Is such confusion 

 intended? The experiments described on conduction 

 .-md radiation are novel, use being made of an indi- 

 cating paint prepared by Mr. Walter Jamieson. This 

 jiaint, which is colourless at ordinary temperatures, 

 turns green when heated, the green colour disappear- 

 ing on cooling. The range of sensitiveness may be 

 from 80° C. to 21° C. Objection must be raised to 

 the designation of the curve in the diagram on p. 82 

 as " heat-curve." Temperature-gradient would be 

 better. We must disagree with the remark on p. 42, 

 footnote ; it is certain a boy will be more readily con- 

 vinced of the anomalous expansion of water by use of 

 the apparatus described in the text (previously de- 

 scribed by Mr. H. E. Hadley in the School World for 

 June. 1901) than by the performance of Hope's experi- 

 ment. The diagram of the constant volume air 



XO. 2004, VOL. 77] 



thermometer on p. 53 is unnecessarily complicated, and 

 does not appear any more exact than that on p. 50. 



The third year's course is devoted entirely to optics, 

 and is similar in plan to the manual on heat. There 

 are upwards of fifty experiments which may be per- 

 formed with simple apparatus, and the book contains 

 many supplementary exercises and questions. Experi- 

 ments 6, 7, 8, pp. 1 1-19, on photometry are mislead- 

 ing, viz., "To find the relation between the illu- 

 minating power and the distance of sources of light." 

 The " intensity of illumination " at a point due to a 

 given source will vary with the distance, but the 

 " illuminating power " of the source remains the 

 same. 



OUR BOOK SHELF. 



The Mechanism of Speech. Lectures delivered before 

 the American Association to promote the Teaching 

 of Speech to the Deaf by Alexander Graham Bell. 

 Second edition. Pp. xv + 133. (New York and 

 London : Funk and Wagnall's Company, 1907.) 

 Price 1.20 dollars net. 

 This is the second edition of a work already re- 

 viewed in X.nuRE, December 27, 1906 (vol. Ixxv., p. 

 196). The first edition was printed during the 

 author's absence in Europe, and he had no oppor- 

 tunity of revising the proofs. As the printers could 

 scarcely be expected to be familiar with the somewhat 

 complicated symbols used by the author's father, 

 Melville Bell, a number of typographical mistakes 

 had crept in. These have now been corrected. A full 

 account is given of Mr. Melville Bell's ingenious 

 system of symbols, which are intended to express the 

 position of various parts of the vocal apparatus in 

 the production of articulate sounds, and illustrations 

 are afforded of the methods by which deaf children 

 can be led to understand the meaning of these sym- 

 bols, and are thus guided in the operation of placing 

 their vocal organs in the position required for a given 

 word. By patient training and by following the 

 judicious maxims of Mr. Graham Bell a wonderful 

 degree of success has been attained in the education 

 of the deaf. 



Mr. Melville Bell's symbols express words, not in 

 letters, nor in the wave vibrations revealed by the 

 phonograph or gramophone, but in forms that in- 

 dicate precisely the physiological position of the arti- 

 culating mechanism necessary for the production of 

 a given sound. A first glance at these strange 

 symbols gives one the impression of the system being 

 too complex for practical purposes, but with the aid 

 of Mr. Graham Bell's instructions it soon becomes 

 easy. The writer in a short time found that he could 

 both write and interpret the symbols. One can 

 readily see how the system might be of use to 

 travellers, as, by means of the symbols, they could 

 write down the sounds of an unknown tongue and 

 reproduce them. .\ knowledge of this system and 

 the use of a phonograph would be invaluable to those 

 who desire to register the articulate expressions of 

 savage tribes. John G. McKendrick. 



The Moths of the British Isles. By Richard South. 

 First Series, containing the Families Sphingidae to 

 Noctuidae. Pp. vi + 343, plates 159, text-figures 24. 

 (London : F. \\'arne and Co., 1907.) Price 7s. 6d. 

 net. 

 Books on British butterflies and moths are now 

 plentiful enough, but we have never seen any which 

 have pleased us so well as the series of which this 

 book is the second volume. It is true that technical!- 



