XOVEMBEB 20, 1903.] 



SCIENCE. 



6GI 



port, but, unfortunately, neither the boat 

 nor the apparatus could be brought from 

 Scotland in time for the experiments. Pro- 

 fessor Pernter demonstrated the formation 

 of vortex-rings on a large scale in the open 

 air by firing a conical cannon, such as is 

 used in some parts of Europe to disperse 

 hail-storms. While the eflfieac.y of the pro- 

 cess is doubtful, yet in the Southport ex- 

 periments the smoke-rings issuing from 

 the cannon, which was placed horizontally 

 instead of vertically, could be both seen 

 and heard in their passage through the air 

 for a distance of several hundred feet. 



A visit was paid by the International 

 Committee to the Fernley Observatory in 

 Hesketh Park, established by ^Ir. J. Bax- 

 endell, Sr., and now maintained by the 

 borough of Southport. This observatory, 

 ■which is one of the best equipped in Great 

 Britain, has an auxiliary station, provided 

 with Mr. Dines' anemometers, situated 

 near the coast. Excursions were made to 

 the Stonyliurst College Observatory, near 

 "VMialley, Lancashire, and also to the Phys- 

 ical Laboratory of the Owens College in 

 Manchester. About sixty meteorologists 

 sat down to their annuad breakfast, in ac- 

 cordance with a custom inaugurated some 

 thirty years ago. The meeting terminated 

 on September 16 with a brilliant banquet 

 to more than one hundred persons, which 

 was given by the mayor of Southport, ]\Ir. 

 Scarisbrick, at his residence. Greaves Hall, 

 in honor of Sir Norman Loekj-er, president 

 of the British Association and Professor 

 Mascart, president of the International 

 Meteorological Committee. 



A. Lawrence Rotch. 



Blue Hill Meteorological Obsehvatorv. 

 October 30, 1903. 



SCIENTIFIC BOOKS. 

 Manual of Advanced Optics. By C. Rigborg 

 Manx. Chicago, Scott, Forsemann & Co. 

 1902. Pp. 193. 

 As the author states in the preface, this 



manual is the basis of the advanced laboratory 

 course in optics in the University of Chicago, 

 and represents contributions from various in- 

 structors. Naturally, it deals rather exten- 

 sively with interference and the applications 

 of interference methods. 



The opening chapter presents, in a very 

 simple manner, the important but generally 

 neglected theory of the limit of resolution of 

 a telescope. Chapter II. extends this theory 

 to the case of two slit apertures before a lens 

 for both single and double line sources. The 

 experimental illustrations make clear the pos- 

 sibility of measuring the angular size of a 

 source and the angular distance between two 

 line sources, but do not suggest the application 

 of this method to astronomical problems. Ref- 

 erence is not made to Rayleigh's theory of, 

 and experiments with, the central stop. The 

 third chapter, on Fresnel's mirrors, contains 

 diagrams, familiar to all of Professor Michel- 

 son's students, illustrating the evolution from 

 the earlier forms of interference apparatus to 

 the modern interferometer. The theory and 

 experiments in this chapter and in the follow- 

 ing one on Fresnel's biprism take up seventeen 

 pages of the text, relatively a large part when 

 the grating is treated in eight pages. 



Chapters V. and VI. contain Michelson's 

 theory of the interferometer and its elegant 

 applications. The presentation is very clear 

 and the contents complete. The gathering 

 together of material from little-used sources 

 bearing upon the interferometer method, 

 probably the most powerful and yet simple 

 method we know in accurate measurement, 

 makes this manual a valuable one to place in 

 the hands of a student. 



The arrangement of the material in Chap- 

 ters VI. and VII. is out of the ordinary. For 

 in the earlier chapter the author deals with a 

 very modern, complex, perhaps forced, method 

 of analyzing an approximately homogeneous 

 radiation, while in the later chapter he pre- 

 sents the well-known prism method of an- 

 alyzing a spectrum. The theory of Chapter 

 Vn. follows the methods of geometrical optics. 

 Rayleigh's simple method of obtaining the dis- 

 persive power of a prism is not given. 



