ADDRESS. 25 



aflfect our senses. When they are used in the attempt to penetrate deeper 

 into the secrets of Nature it is more than probable that they will meet 

 with insuperable barriers, but this fact does not demonstrate that the 

 fundamental assumptions are false, and the question as to whether any 

 particular obstacle will be for ever insupei'able can rarely be answered 

 with certainty. 



Those who belittle the ideas which have of late governed the advance 

 of scientific theory too often assume that there is no alternative between 

 the opposing assertions that atoms and the ether are mere figments of the 

 scientific imagination, or that, on the other hand, a mechanical theory of 

 the atoms and of the ether, which is now confessedly imperfect, would, if 

 it could be perfected, give us a full and adequate representation of the 

 underlying realities. 



For my own part I believe that there is a via media. 



A man peering into a darkened room, and describing what he thinks 

 he sees, may be right as to the general outline of the objects he discerns, 

 wrong as to their nature and their precise forms. In his description fact 

 and fancy may be blended, and it may be difficult to say where the one 

 ends and the other begins ; but even the fancies will not be worthless if 

 they are based on a fragment of truth, which will prevent the explorer 

 from walking into a looking-glass or stumbling over the furniture. He 

 who saw ' men as trees walking ' had at least a perception of the funda- 

 mental fact that something was in motion around him. 



And so, at the beginning of the twentieth century, we are neither 

 forced to abandon the claim to have penetrated below the surface of 

 Nature, nor have we, with all our searching, torn the veil of mystery 

 from the world around us. 



The range of our speculations is limited both in space and time : in 

 space, for we have no right to claim, as is sometimes done, a knowledge 

 of the ' infinite universe ' ; in time, for the cumulative efiiects of actions 

 which might pass undetected in the short span of years of which we have 

 knowledge, may, if continued long enough, modify our most profound 

 generalisations. If some such theory as the vortex-atom theory were 

 true, the faintest trace of viscosity in the primordial medium would ulti- 

 mately destroy matter of every kind. It is thus a duty to state what 

 we believe we know in the most cautious terms, but it is equally a duty 

 not to yield to mere vague doubts as to whether we can know anything. 



If no other conception of matter is possible than that it consists 

 of distinct physical units — and no other conception has been formu- 

 lated which does not blur what are otherwise clear and definite out- 

 lines —if it is certain, as it is, that vibrations which cannot be propagated 

 by ordinary matter travel through space, the two foundations of physical 

 theory are well and truly laid. It may be granted that we have not yet 

 framed a consistent image either of the nature of the atoms or of the 

 ether in which they exist ; but I have tried to show that in spite of the 



