2 NATURE 

‘ [January € be es ; 

the means of original publication of some of the writings 
of Galileo. In physical science Huygens was one of an 
illustrious international company which included his 
contemporary Newton, and ranks next among his 
peers both in dynamics and. in optics. - In our own 
days the eminence of Holland in physical science is 
maintained by H. A. Lorentz, H. Kamerlingh Onnes, 
P. Zeeman, and others of a brilliant band who have 
been, in the main, products of the great University 
of Leyden which dates from the times of national 
revival. 
In his early days contemporaries in this country to 
whom Dutch sources were not very accessible owed 
their knowledge of Prof. Lorentz’s writings mainly to 
expositions and discussions by a kindred spirit the late 
Lord Rayleigh, and subsequently by Lodge in con- 
nexion with his thorough experimental scrutiny of the 
relation of the Earth’s motion to the aether, regarded 
as the seat of propagation of the rays of light by which 
we explore the universe. No trace could be anywhere 
found of exception to the principle that Lorentz 
favoured as the basis of optical theory, that the aether 
is a stationary medium: material bodies must thus 
be structures of molecular texture so open that, in the 
simile of Thomas Young when he pleaded in 1800 for 
a revival of the wave theory of Huygens, the aether 
penetrates through moving matter as freely as the 
wind through a grove of trees. The republication of 
some of Prof. Lorentz’s early investigations, in which 
historical exposition and criticism are so happily 
blended with new advance, in vol. i. of his ‘‘ Abhand- 
lungen iiber theoretische Physik” in 1907 revealed, 
at any rate to one student, how much research into 
sources might have been saved him by earlier access to 
the Archives néerlandaises of 1887.1 The volume also 
presented much unpublished material. There is for 
example a treatise on the Second Law of Thermo- 
dynamics and its relation to Molecular Theory, pp. 
202-298. Nothing could be more valuable, for students 
who desire a real grasp of this fascinating subject, than 
connected exposition by a master, on general lines 
freed from excursions into detail. 
This work was doubtless even fresher then than now, 
when the principles the scope of which is so universal 
have been sifted and refined in all directions in so many 
essays and text-books. The power and simplicity of 
the foundations of pure thermodynamics have at all 
times been a magnet to the most powerful minds, from 
Kelvin who persisted with the prescience of genius in 
hunting out and rediscovering in Paris the master 
tract of Sadi Carnot, down through Clausius, Maxwell, 
Helmholtz, Willard Gibbs. One can recall the crucial 
» “Jnfluence du mouvement de la terre sur les phénoménes lumineux”’: 
Abhandlungen, i. pp. 341-304. 
NO. 2775, VOL. 111] 
fundamental concept of Available, in contrast with 
Dissipated, Energy, introduced in a fragmentary way 
by Kelvin, whose wealth of fresh thoughts and of 
practical interests scarcely ever allowed him a chance 
of systematically developing any subject ; its relation 
to the more convenient analytical concept of Entropy 
introduced by Clausius, and its physical elucidation 
in terms of a science of molecular statistics by Boltz- 
mann and Gibbs; the luminous expositions and 
developments of Rayleigh; the theoretical outlook 
of Gibbs, vast enough to predict a full-blown new 
science of Physical Chemistry before it had come to 
birth ; even such questions of pure logic as the intimate 
essential connexion of the principle of Carnot with 
the identification of heat as energy which came finally 
twenty years later. One remembers a remark of Prof. 
Lorentz in relation to an obituary exposition of Kelvin’s 
early activity, that he had not been aware that this 
side of the subject had been so fully grasped at that 
early date. 
In this historical feeling which has led Prof. Lorentz 
so frequently to interweave his own contributions to 
knowledge into a reasoned analysis of the actual 
position of the science at the time, close affinity may 
be traced with the work of Lord Rayleigh. For both 
of them, perhaps especially for the latter, an essential 
interest of human learning is the story of its historical _ 
evolution: nothing is so attractive as to recognise, 
still more to discover, the early insight of genius into 
problems usually thought to belong to later times. 
To both of them it appears. to have been at least as 
congenial to explore and improve a wide field of know- 
ledge, as to engage in strenuous special calculations 
such as are the very essence of progress in dynamical 
astronomy : though neither of them shirked such tasks 
when they presented themselves. Perhaps nowadays 
appreciation of the past is more than ever necessary to 
balance the haste of the present. 
Of late years Prof. Lorentz’s activity has been much 
turned by public demands into the direction of formal — 
courses of lectures at University centres, in which his 
own thoughts and ideas are happily embedded. Thus 
the standard treatise on the Theory of Electrons 
arose out of lectures at Columbia University, New 
York, in 1905 ; several courses have been published in 
German ; and a most interesting and concise reasoned 
account of the state of knowledge and speculation 
regarding statistical thermodynamic theories, leading 
up through Brownian movements and local fluctua- 
tions of energy into the mysteries of quanta, delivered — 
at the Collége de France in 1912, came to be issued in 
French from Leipzig with additional notes in the year 
1916. Earlier discussions on this latter subject 
(Abhandlungen, vol. i.) followed the lines developed also 
