I2.S MODERN TENDENCY OF PHYSICAL SCIENCE. 



energy, and readily assimilating the sceptical utterances of those 

 whom I have for the nonce described as mathematicians, though 

 it is but an active group or school of mathematicians who take 

 this line. 



" And Physicists, or some of them, are seeking to dispense 

 with Newton's laws of motion, to supersede that dynamical basis 

 on which they have built for so long, to regard all laws as merely 

 conveniences of expression, and are trying if they can manage 

 to sustain their science on a basis of action at a distance, fluid 

 electricity, corpuscular light, and caloric heat. 



" Discoveries are of two chief kinds — the discovery of law 

 and the discovery of fact. The two tend to become inextricably 

 interwoven : the discovery of law often leads to the discovery of 

 new facts, and the discovery of new facts to either the formula- 

 tion of new laws or new modes of statement, or to the resuscita- 

 tion of discarded ones. 



" As examples of the discovery of law, I instance Newton's 

 gravitational theory of astronomy, and Maxwell's electromagnetic 

 theory of light. Discoveries of this kind take their place among 

 the most prodigious efforts of the human intellect. 



" Of all the facts discovered during the last half-century, I 

 suppose that Rontgen's A-rays excited the most popular astonish- 

 ment ; and certainly they were sufficiently new. Nevertheless, 



existing theory had a place for them If called upon to 



compare the discovery of Rontgen with the discovery of Bec- 

 qnerel, I should give the palm of novelty to the latter; for the 

 spontaneous splitting up of atoms, and the consequent expulsion 

 of constituent fragments, was not provided for on any theory. 

 It was a revolutionary new fact. 



" It is needless to emphasise the extraordinary suggestive- 

 ness which the instability and intense energy of atomic structure, 

 thus demonstrated, confers upon our ideas of material atoms in 

 general, since it is surely probable that the stability of the atom 

 of the better-known elements, especially of the heavy ones like 

 lead, mercury, and gold, is. after all, only a question of degree. 

 Some substances last a few minutes, others a few weeks or 

 years, some centuries, and others millions of aeons — these last 

 being naturally more plentiful, like a population with a low death- 

 rate — yet it must surely be considered unlikely that any such 

 atomic groupings are so devoid of internal energy as to be 

 endowed with an absolutely permanent structure incapable of 

 further subdivision. 



" So far, it has all seemed plain sailing; but now has come 

 the era of scepticism, and an attempt to limit science to purely 

 material entities and to reduce Physics to a sort of glorified 

 Chemistry, to return, in fact, to the kind of ideas which prevailed 



