Notices respecting New Books. 569 
discontinuity and the discontinuity in Y are intimately con- 
nected. Is it not a possible explanation of Lord Rayleigh's 
and Prof. Bohr's different experiences, that the carefully 
dried tubes of the latter may have developed a high state of 
electrification by the motion of the mercury, and that thus 
the gas became subject to electrical disturbances sufficient to 
effect the transition from one molecular state to the other ? 
These experiments were made in the laboratory of Prof. 
J. S. Townsend, Wykeham Professor of Physics, Oxford. 
LIII. Notices respecting New Boohs. 
Condensation of Vapor as induced by Nuclei and Ions. By 
Caul Bakcs, Hazard Professor of Physics, Brown University. 
"Washington: Published by the Carnegie Institution. 1907. 
Pp. ix+164. 
TN this monograph the author, whose work on nuclei is well 
-*- known, describes a number of investigations carried out with 
his fog-chamber apparatus. The apparatus having been sufficiently 
improved, it was used for various experiments, including the 
growth of persistent nuclei, the production of water nuclei by 
evaporation, the results obtained when X-rays are allowed to 
strike the fog-chamber from different distances, the effect due to 
radium, &c. Other problems dealt with in the book are the dis- 
tribution of colloidal nuclei and of ions in media other than air- 
water, the simultaneous variation of the nucleation and the 
ionization of the atmosphere of Providence, and the variations of 
the colloidal nucleation of dust-free air in course of time. 
Fourier's Series and Integrals. By H. S. Cakslaw. Macmillan 
and Co. London and New York. 1906. 
The complete title is " Introduction to the Theory of Pourier's 
Series and Integrals and the Mathematical Theory of the Conduction 
of Heat." The book naturally falls into two parts, Part I. being 
concerned with the purely mathematical developments, and Part II. 
with the applications to the various practical and ideal problems 
of heat conduction. Basing on the modern theory of rational and 
irrational numbers, Professor Carslaw leads up through a logical 
discussion of the convergence of infinite series to the important 
forms associated with the name of Pourier, finishing in Chapter VIII. 
with the Integrals. This part occupies 187 pages in a book of 
•130 pages. The remainder is devoted to the problems of thermal 
conduction. Professor Carslaw is to be congratulated on sup- 
plying a book which cannot fail to be of great service to several 
classes of readers. The student of pure mathematics will find 
his mind directed along the best modern lines of investigation of 
