266 



NATURE 



[July 19, 1900 



charge, and if consequently we must look to some other, 

 possibly accidental, cause for Rowland's observation, it 

 will certainly revolutionise the whole modern treatment 

 of electro-magnetism. The question raised by this ex- 

 periment is, any way, one of the most fundamental ones 

 in the connection between ether and matter, and it is to 

 be hoped that this question will be settled soon in a 

 conclusive way, either by showing that M. Cremieu's 

 conclusion is not justified by his observation that his ex- 

 periment really confirms a complete theory, or by over- 

 throwing all our existing views, and leaving a free field 

 for the twentieth century to build a new theory of 

 electro-magnetism on a firmer foundation. 



In discussing the result of Michelson and Morley's 

 experiments, from which they concluded that the ether 

 is carried along by the earth in its motion, Mr. Larmor 

 shows that such a hypothesis is quite inconsistent 

 with the fact of aberration and with the unten- 

 ability of Sir George Stokes's suggestion that ether is 

 like a very soft jelly. How such a soft material could be 

 the means by which tramcars are driven by shearing 

 stresses seems an additional difficulty in the way of this 

 suggestion. Mr. Larmor concludes that the stone sup- 

 port on which the mirrors were borne changed in its 

 dimensions, as it was rotated, by an amount proportional 

 to the square of the ratio of its velocity to the velocity of 

 light, and he justifies this by showing that if matter con- 

 sists of clusters of electrons, just such a change of 

 dimensions would take place as the experiment shows to 

 take place. There is some difficulty in the hypothesis 

 that the inertia of matter, or any large part of it, is like 

 that of electrons and due to the motion of the neigh- 

 bouring ether, because this involves the supposition that 

 the inertia would change with the distance between the 

 component electrons. That there may be some very 

 minute eflfect of this kind is quite possible, though as yet 

 undiscovered, but that any large effect of the kind exists 

 seems extremely improbable. Possibly a careful study 

 of the accuracy of Kepler's laws as applied to the solar 

 system might show some discrepancy depending on a 

 difference between the average distance of the electrons 

 in such different materials as probably constitute 

 Neptune and Mercury. 



A previous question to all our explanations of pheno- 

 mena by analytical dynamics is raised by Mr. Larmor in 

 Appendix B, " On the Scope of Mechanical Explanation : 

 and on the Idea of Force." He has utilised the principle 

 of least action throughout his work, and this appendix is 

 a justification of his doing so, and besides raises questions 

 as to the applicability of dynamical explanation to the 

 growth and decay of vital organisms. Hertz objected to 

 the adequacy of the principle of least action as a complete 

 solution of all possible dynamical systems, because it is 

 not generally applicable when rolling takes place, and we 

 cannot be sure that rolling may not be one of the funda- 

 mental facts of the dynamics of the ether. Mr. Larmor 

 dismisses this objection on the doubtful ground that 

 '^ rolling is foreign to molecular dynamics." Hertz had 

 also objected to the principle of least action for the 

 semi-metaphysical reason that it makes the present state 

 of the system depend on the future as well as on the 

 past. As Mr. Larmor himself uses in his work the 

 vector potential which makes the state at each place 

 NO. 1603, VOL. 62] 



depend on what is simultaneously occurring at all parts 

 of the universe, he naturally finds no objection to the 

 principle of least action, because it makes the present de- 

 pend on all future time. Neither of these methods is 

 unobjectionable ; each is an analytical juggle, which has 

 to be most carefully guarded lest it lead us into mistakes. 

 The way in which the vector potential apparently locates 

 the energy in the current instead of in the magnetic field 

 outside it is a most serious objection to its use, although 

 Mr. Larmor seems to have steered clear of the difficulties 

 raised by this curious complication. In a similar way the 

 principle of least action is open to the objection of Hertz; 

 of making the present apparently depend on the future 

 to an extent that does not apply to his own principle of 

 the straightest path. It is a question for consideration in 

 connection with Mr. Larmor's discussion on the applic- 

 ability of dynamics to vital phenomena whether the 

 possibility of determining our actions by considerations 

 as to the future is not connected with the possibility of 

 analytically expressing the dynamics of the present by a 

 formula which involves the future. 



It will, from this meagre review, be evident that Mr. 

 Larmor's treatise raises most fundamental and interesting 

 questions, and is one that all who desire to strengthen the 

 foundations of our knowledge of nature should carefully 

 study. Geo. Fras. FitzGerald. 



LAND RECLAMATION. 

 The Reclamation of Land from Tidal Waters. By 

 Alexander Beazeley, M.Instit.C.E. Pp. xii + 314. 

 (London : Crosby Lockwood and Son, 1900 ) 



THE area of this country is gradually diminishing by 

 the continual waste that is going on all round the 

 coast. On the Yorkshire coast it is estimated that two 

 miles have disappeared since the Roman occupation ; and 

 more modern records show that towns and villages have 

 disappeared with their houses and churches, and in some 

 cases the whole parish has been washed away. Along 

 the Norfolk coast the only record of several villages is^ 

 " washed away by the sea " ; and on the Kentish coast,, 

 churches and houses have fallen down the cliffs, or» 

 which are to be seen the bones formerly deposited in a | 

 vanishing churchyard. On the south coast, although ! 

 the chalk cliffs at the east end of the English Channel 

 are subject to continual falls and slips, more care has 

 been taken to protect them ; but along the clay cliffs of 

 Dorsetshire the waste is continuous ; here twenty acres 

 slipped down seaward in one night from the cliffs at 

 Axminster. On the west coast, the nets of the fishermea 

 are said to become occasionally entangled with the ruins 

 of houses and buildings buried in the sea some distance 

 from the coast off Blackpool. 



As some compensation for all this loss due to the 

 ever-continuous operations of nature, the energy of ma» 

 has succeeded in reclaiming and recovering a large 

 area of rich cultivatable land in estuaries where rivers 

 have discharged great quantities of detritus picked up 

 along their course. At no time in the history of 

 this country were reclamations carried on to a greater 

 extent than in the time of the Romans, and this is the 

 more remarkable as, compared with the population at 

 that time, land must have been plentiful. It was during 



