August 9, ii>94j 



NA TURE 



341 



families there were blanks left ; places not filled upbecawse the 

 properly constituted elements required according to his theory 

 had not been found to fill them. For the moment their absence 

 seemed a weakne-s in the Professor's idea, and gave an arbitrary 

 aspect to his scheine. But the weakness was turned into 

 strength when, to the astonishment of the scientific world, 

 three of the elements which were missing made their ap- 

 pearance in answer to his call. He had described before- 

 hand the qualities they ought to have ; and gallium, 

 germanium, and scandium, when they were discovered 

 shortly after the publication of his theory, were found to be 

 duly clothed with ilie qualities he required in each. This re- 

 markable confirmation has left MendeleefTs periodic law in an 

 unassailable position. But it has rather thickened than 

 dissipated the mystery which hangs over the elements. The 

 discovery of these co-ordinate families dimly points to some 

 identical origin, without suggesting the method of their genesis 

 or the nature of their common parentage. If they were organic 

 beings all our ditlficuUies would be solved by muttering the 

 comfortable word "evolution" — one of those indefinite words 

 from time to ti iie vouchsafed to humanity, which have the gift 

 of alleviating so many perplexities and masking so many gaps in 

 our knowledge. But the families of elementary atoms do not 

 breed ; and we cannot therefore ascribe their ordered difference 

 to accidental variations perpetuated by heredity under the in- 

 fluence of natural selection. The rarity of iodine, and the 

 abundance of its sister chlorine, cannot be attributed to the 

 survival of the fittest in the struggle for existence. We cannot 

 account (or the minute difference which persistently dis- 

 tinguishes nickel from cobalt, by ascribing it to the recent in- 

 heritance by one of them of an advantageous variation from the 

 parent stock. 



The upshot is that all these successive triumphs of research, 

 Dalton's, Kirchhofl"s, Mendeleeflf's, greatly as they have added 

 to our store of knowledge, have gone but little way to solve the 

 problem which the elementary atoms have for centuries pre- 

 sented to mankind. What the atom of each element is, 

 whether it is a movement, or a thing, or a vortex, or a point 

 having inertia, whether there is any limit to its divisibility, and, 

 if so, how that limit is imposed, whether the long list of elements 

 is final, or whether any of them have any common origin, all 

 these questions remain surrounded by a darkness as profound 

 as ever. The dream which lured the alchemists to their tedious 

 labours, and which may be said to have called chemistry into 

 being, has assuredly not been realised, but it has not yet been 

 refuted. The boundary of our knowledge in this direction re- 

 mains where it was many centuries ago. 



The next discussion to which I should look in order to find 

 unsolved riddles which have hitherto defied the scrutiny of 

 science, would be the question of what is called the ether. The 

 €ther occupies a highly anomalous position in the world of 

 science. It may be described as a half-discovered entity. I 

 dare not use any less pedantic word than entity to designate it, 

 for it would he a great exaggeration of our knowledge if I were 

 to speak o( it as a body or even as a substance. When nearly 

 a century ago Young and Fresnel discovered that the motions 

 of an incandescent panicle were conveyed to our eyes by undu- 

 lation, it followed that between our eyes and the panicle there 

 must be someihing to undulate. In order to furnish that some- 

 thing, the notion of the ether was conceived, and for more than 

 two generations the main, if not the only, function of the word 

 ether has been to furnish a nominative case to the verb " to undu- 

 late." Lately, our conception of this entity has received a notable 

 extension. One of the mo^t brilliant of the services which 

 Prof. Maxwell h.is rendered to science has been the discovery 

 that the figure which expressed the velocity of light, also ex- 

 pressed the multiplier required to change the measure of static 

 or passive electricity into that of dynamic or active electricity. 

 The interpretation reasonably alfixed to this discovery is that, 

 as light and the electric impulse move approximately at the 

 .■■ame rate through space, it is probable that the undulations 

 which convey them are undulations of the same medium. .\nd 

 as induced electricity [)enetrates through everything, or nearly 

 everything, it follows that the ether through which its undula- 

 tions are propag ned must pervade all space, whether em])ly or 

 full, whether occupied by opaque matter or transparent matter, 

 or by no matter at all. The attractive experiments by which 

 the late Prof. Hertz illustrated the electric vibrations of the 

 ether will only be allude<l to by me, in order that I may express 

 ■the regret deeply and generally felt that death should nave ter- 



NO. 1293, VOL. 50] 



minated prematurely the scientific career which had begun with 

 such brilliant promise and such fruitful achievements. But the 

 mystery of the ether, though it has been made more fascinating 

 by these discoveries, remains even more inscrutable than before. 

 Of this all-pervading entity we know absolutely nothing except 

 this one fact, that it can be made to undulate. Whether 

 outside the influence of matter on the motion of its waves, 

 ether has any effect on matter or matter upon it, is abso- 

 lutely unknown. And even its solitary function of un- 

 dulating ether performs in an abnormal fashion which 

 has caused infinite perplexity. All fluids that we know 

 transmit any blow they have received by waves which undulate 

 backwards and forwards in the path of their own advance. The 

 ether undulates athwart the path of the wave's advance. The 

 genius of Lord Kelvin has recently discovered what he terms a 

 labile state of equilibrium, in which a fluid that is infinite in its 

 extent may exist, and may undulate in this eccentric fashion 

 without outraging the laws of mathematics. I am no mathe- 

 matician, and I cannot judge whether this reconciliation of the 

 action of the ether with mechanical law is to be looked upon as 

 a permanent .'■olution of the question, or is only what diploma- 

 tists call a modus vivenJi. In any case it leaves our knowledge 

 of the ether in a very rudimentary condition. It has no known 

 qualities except one, and that quality is in the highest degree 

 anomalous and inscrutable. The extended conception which 

 enables us to recognise ethereal waves in the vibrations of elec- 

 tricity has added infinite attraction to the study of those waves, 

 but It carries its own difficulties with it. It is not easy to fit in 

 the theory of electrical ether waves with the phenomena of 

 positive and negative electricity, and as to the true significance 

 and cause of those counteracting and complementary forces, to 

 which we give the provisional names of negative and positive, 

 we know about as much now as Franklin knew a century and a 

 half ago. 



I have selected the elementary atoms and the ether as two 

 instances of the obscurity that still hangs over problems which 

 the highest scientific intellects have been mvestigating for several 

 generations. A more striking but more obvious instance still is 

 Life — animal and vegetable Life — the action of an unknown 

 force on ordinary mailer. What is the mysterious impulse 

 which is able to strike across the ordinary laws of matter, and 

 twist them for a moment from their path? Some people demur 

 to the use of the term " vital force " to designate this impulse. 

 In their view the existence of such a force is negatived by the 

 fact that chemists have been able by cunning substitutions to 

 produce artificially the peculiar compounds which in nature are 

 only found in organisms that are or have been living. These 

 compounds are produced by som£ living organism in the per- 

 formance of the ordered series of functions proper to its brief 

 career. To counterfeit them — as has been done in numerous 

 cases — does not enable us to do what the vital force alone can 

 effect — to bring the organism itself into existence, and to cause 

 it to run its appointed course of change. This is the unknown 

 force which continues to defy not only our imitation but our 

 scrutiny. Biology has been exceptionally active and successful 

 during the last half-century. Its triumphs have been brilliant, 

 and they have been rich enough not only in immediate result 

 but in the promise of future advance. Vet they give at present 

 no hope of penetrating the great central ir.ystery. The pro- 

 gress which has been made in the study of microscopic life has 

 been very striking, whether or not the results which are 

 at present inferred from it can be taken as conclu- 

 sive. Infinitesimal bodies found upon the i-oots of 

 plants have the proud oflice of capturing and taming 

 for us the free nitrogen of the air, which, if we are 

 to live at all, we must consume and assimilate, and yet which, 

 without the help of our microscopic ally, we could not draw for 

 any useful purpose from the ocean of nitrogen in which we 

 lire. Microscopic bodies are convicted of causing many of the 

 worst diseases to which flesh is heir, and the guilt of many more 

 will probably be brought home to them in due time ; and they 

 exercise a scarcely less sinister or less potent influence on our 

 race by the plagues with which they destroy some of the most 

 valuable fruits of husbandry, such as the potato, the mulberry, 

 and the vine. Almost all their power resides in the capacity of 

 propagating their kind with infinite rapidity, and up to this 

 time science has been more skilful in describing their ravages 

 than in devising means to hinder them. It would be ungratelul 

 not to mention two brilliant exceptions to this criticism. The 

 antiseptic surgery which we owe chiefly to Lister ; and the in- 



