1 86 CONTINUITY. 



discourse on ; that word is continuity no new word, and used 

 in no new sense, but perhaps applied more generally than it 

 has hitherto been. We shall see, unless I am much mistaken, 

 that the development of observational, experimental, and even 

 deductive knowledge is either attained by steps extremely 

 small and forming really a continuous march ; or, when 

 distinct results apparently separate from any co-ordinate phe- 

 nomena have been attained, that then, by the subsequent 

 progress of science, intermediate links have been discovered 

 uniting the apparently segregated instances with other more 

 familiar phenomena. We shall see that the more we inves- 

 tigate, the more we find that in existing phenomena graduation 

 from the like to the seemingly unlike prevails, and in the 

 changes which take place in time gradual progress is, and 

 apparently must be, the course of nature. 



Let me now endeavour to apply this view to the recent 

 progress of some of the more prominent branches of science. 



In Astronomy, from the time when the earth was consi- 

 dered a flat plain bounded by a flat ocean when the sun, 

 moon, and stars were regarded as lamps to illuminate this 

 plain each successive discovery has brought with it similitudes 

 and analogies between this earth and many of the objects of 

 the universe, with which our senses, aided by instruments, 

 have made us acquainted. I pass, of course, over those dis- 

 coveries which have established the Copernican system as 

 applied to our sun, its attendant planets, and their satellites. 

 The proofs, however, that gravitation is not confined to our 

 solar system, but pervades the universe, have received many 

 confirmations by the labours of members of this Association. 

 I may name those who have held the office of President, Lord 

 Rosse, Lord Wrottesley, and Sir J. Herschel, the two latter 

 having devoted special attention to the orbits of double stars, 

 the former to those probably more recent systems called 

 nebulae. Double stars seem to be orbs analogous to our own 

 sun, and revolving round their common centre of gravity in a 

 conic-section curve, as do the planets with which we are more 

 intimately acquainted ; but the nebulae present more difficulty, 

 and some doubt has been expressed whether gravitation, as 

 we understand it, acts with those bodies (at least those exhi- 



