REVIEWS 



Mathematical and Physical Papers of Sir William Thomson, Lord Kelvin. 



Vol. iv. Hydrodynamics and General Dynamics. Arranged, revised, and 

 annotated by Sir Joseph Larmor. [Pp. xvi + 563.] (Cambridge University 

 Press, 1910. Price i8j.) 



The first three volumes of the Mathematical and Physical Papers of Sir William 

 Thomson were published in the lifetime of the author, who also began the 

 preparation of vol. iv. ; the papers collected by him for this volume were 

 published however as an appendix to the Baltimore Lectures. In the first three 

 volumes the papers were printed in chronological order, but in this volume they 

 have been grouped under subjects. Some of the papers continuing the sequence 

 of the first three volumes had been published, as mentioned above, so that the 

 original scheme could hardly be continued ; and bringing together the papers 

 dealing with one subject has distinct advantages. The time has probably not 

 yet come when it is possible to say which place Lord Kelvin occupies amongst 

 the great Natural Philosophers and Mathematicians of the world, but as one 

 peruses the papers of this and the preceding volumes — there is another to 

 follow — one feels how versatile and great the man was and that to him is assured 

 a very high place amongst the immortals. 



Addressing the British Association in 1871 Sir William Thomson remarked : 

 " Maxwell has completed the dynamical explanation of the known properties of 

 gases except their electric resistance and brittleness to electric force ; but definite 

 and complete as is Maxwell's theory, it is but a well-drawn chart in which all 

 physical science would be represented with every property of matter shown in 

 dynamical relation to the whole. But there could be no satisfaction to the mind 

 in describing precisely the relation of the states of matter when the properties 

 of the atom are assumed." Long before this famous utterance the mind of 

 Thomson was searching after a comprehensive theory of matter, which not only, 

 as Larmor says in his Ether and Matter, " can be formulated as a scheme of 

 differential equations," but of which he could also imagine a model. 



Helmholtz, in his epoch-making memoir " On the Integrals of the Hydro- 

 dynamic Equations which express (Wirbelbewegung) Vortex Motion," had as early 

 as 1858 investigated the laws of whirlpool or vortex motion in a perfect fluid and 

 had shown that once vortex motion has been set up it is permanent and that 

 there is an unchanging relation between the rotation and the portion of the fluid 

 acquiring the motion. Nine years later Tait had translated this remarkable 

 memoir and devised the ingenious and well-known experiments with smoke-rings 

 to illustrate the theory. On seeing these experiments Thomson saw the pos- 

 sibility that the vortex rings of Helmholtz may be the only true atoms, and the 

 papers in the first section of this book are reprints of his papers on Vortex 

 Motion, in which he developes the hypothesis "that space is continuously occupied 

 by an incompressible frictionless liquid acted on by no force, and that material 

 phenomena of every kind depend solely on motions created in the liquid." 



153 



