THE STORY OF NINETEENTH-CENTURY SCIENCE 



it. Once planted victoriously on the conquered ram- 

 parts, the hypothesis becomes a theory a generaliza- 

 tion of science marking a fresh coign of vantage, which 

 can never be successfully assailed unless by a new host 

 of antagonistic facts. Such generalizations, with the 

 events leading directly up to them, have chiefly occu- 

 pied our attention. 



But a moment's reflection makes it clear that the bat- 

 tle of science, thus considered, is ever shifting ground 

 and never ended. Thus at any given period there are 

 many unsettled skirmishes under way ; many hypoth- 

 eses are yet only struggling towards the strongholds of 

 theory, perhaps never to attain it ; in many directions 

 the hosts of antagonistic facts seem so evenly matched 

 that the hazard of war appears uncertain ; or, again, so 

 few facts are available that as yet no attack worthy the 

 name is possible. Such unsettled controversies as these 

 have, for the most part, been ignored in our survey of 

 the field. But it would not be fair to conclude our 

 story without adverting to them, at least in brief ; for 

 some of them have to do with the most comprehensive 

 and important questions with which science deals, and 

 the aggregate number of facts involved in these unfin- 

 ished battles is often great, even though as yet the 

 marshalling has not led to final victory for any faction. 

 In some cases, doubtless, the right hypothesis is actually 

 in the field, but its supremacy not yet conclusively 

 proved perhaps not to be proved for many years or 

 decades to come. Some of the chief scientific results of 

 our century have been but the gaining of supremacy for 

 hypotheses that were mere forlorn hopes, looked on 

 with general contempt, if at all heeded, when the eigh- 

 teenth centur}' came to a close witness the doctrines of 



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