56 Scientific Intelligence. 



the shape of the orifice of the supply tube so that the area of the 

 efflux stream should be proportional to the sidewise displacement 

 of the disk. The idea was carried out by choosing a rectangular 

 orifice for the supply i)ipe and calculating such a shape for the 

 hole in the plate that it should produce a harmonic disturbance 

 for the sound vibrations. A disk was constructed with the 

 irregular' shaped hole indicated by the calculations, and the 

 experimental tests showed a very satisfactory improvement in 

 the resulting tone. At a low frequency of from 80 to 90 vibra- 

 tions per second the ratio of the intensity of the octave to the 

 fundamental was only 30 per cent, which is a reduction of the 

 intensity of the first harmonic to about one seventh of its value 

 in the Seebeck siren. At a frequency of 350 vibrations the octave 

 was found to possess only 6 per cent, of the intensity of the 

 fundamental which is a notable gain for the new design. — Proc. 

 Roy. Soc. 98, 414:, 1921. f. e. b. 



8. An Introduction to Technical Electricity ; by S. G. Star- 

 ling. Pp. xii, 181. London 1921 (Macmillan and Co.). — This 

 is one of the Life and Work Series, a book of a new type designed 

 to meet the requirements of elementary instruction in continua- 

 tion and vocational schools. The writer is well known as the 

 author of what is perhaps the best mathematical treatise on 

 Electricity and Magnetism in the language. 



In the present work however the treatment is developed from 

 the purely experimental side and requires no mathematical knowl- 

 edge beyond multiplication and division. The subject is 

 approached by the study of the magnetic effect of a current pro- 

 duced by a simple cell and its application in the electric bell and 

 the telegraph sounder. This is followed by experiments on mag- 

 nets and a description of magnetic fields arising from various 

 sources. Succeeding chapters explain the generation of the elec- 

 tric current and illustrate its most common and important 

 applications. 



The illustrations are simple and clear and the typography 

 admirable. Experiments, precisely described, are introduced at 

 every stage of the course to secure for the boy actual acquaintance 

 with electrical phenomena, and numerical examples where intro- 

 duced are fully worked out. Each chapter is supplied with a set 

 of exercises for home study by which the solitary learner may test 

 his knowledge. f. e. b. 



II. Geology. 



1. Thirteenth Annual Report, Florida State Geological Sur- 

 vey; 307 pp., 43 text fig's., 1921.— The state geologist, Herman 

 GuNTER, here reports (pp. 1-32) on the activities of the State 

 Geological Survey, and on the mineral production for 1918. 



