200 intelligence and Miscellaneous Articles. 



to find an extensive use made of that method, but we are often 

 confronted with masses of Cartesians. Round each subject is 

 accumulated a great deal of mathematical matter, but sufficient 

 distinction is not made between what is fundamental and what is 

 subordinate. Eor instance, we cannot find anywhere the funda- 

 mental equatious of the electron theory clearly stated and con- 

 trasted with the Maxwellian equatious. It would have added 

 greatly to the value of the book if more care had been taken to 

 secure unity, and to make the explanatory text a logical discussion 

 of basic principles. As it is, there is a great deal of very valuable 

 matter in the book, and as a handbook to the writings of the 

 famous Cambridge school of mathematical physicists it will find an 

 honoured place on many shelves. 



Annuaire du Bureau des Longitudes pour Van 1919. Grautier- 

 Yillars: Paris. Pp. viii + 680. Price 3 francs. 



This excellent little publication contains, in addition to the usual 

 astronomical and geographical information, two valuable articles, 

 one on the figure of equilibrium of a rotating liquid whose elements 

 obey the Newtonian law of attraction, by M. P. Appell, and the 

 other on the determination of the diameter of heavenly bodies by 

 interference methods, by M. Maurice Hamy. The names of the 

 authors vouch for the worth of these short accounts of the work 

 done up to the present on the subject treated. We would also 

 draw attention to the brief resume on solar physics prepared by 

 M. H. Deslandres. 



XVI. Intelligence and Miscellaneous Articles. 



PROBLEMS IN CONDUCTION OF HEAT. 



To the Editors of the Philosophical Magazine. 



~ The University of Sydney, 



Gentlemen, April ^ mQ > 



TT may be worth while to mention that the method of attacking 

 problems in the Conduction of Heat, when the surface 

 temperature varies with the time, attributed to Eiemann in 

 Mr. McLeod's paper (Phil. Mag. ser. 6, vol. xxxvii. Jan. 1919, 

 p. 139), is in fact, due to Duhamel. Reference may be made to 

 the Journal de VEcole Poly technique, T. xiv. Cah. 22, p. 20, 1333, 

 and to my book on ' Fourier's Series,' p. 208. 



Yours faithfully, 



IT. S. Carslaw. 



