EXCEI TIOXAL I HEXOMEXA. 307 



ages two brilliant but temporary stars caused more 

 popular interest in astronomy than any other events, 

 and to one of them we owe all the observations of Tycho 

 Brahe, the mediaeval Hipparchus. 



In other sciences, as well as in that of the heavens, 

 exceptional events are commonly the points from which 

 we start to explore new regions of knowledge. It lias 



J- o o 



been beautifully said that Wonder is the daughter of 



o 



Ignorance, but the mother of Invention ; and though the 

 most familiar and slight events, if fully examined, will 

 afford endless food for wonder and for wisdom, yet it is 

 the few peculiar and unlooked-for events which most often 

 lead a scientific mind into a course of discovery. It is 

 true, indeed, that it requires much philosophy to observe 

 things which are too near to us. 



The high scientific importance attaching, then, to ex 

 ceptions, renders it desirable that we should carefully 

 consider the various modes in .which an exception may 

 be disposed of; while some new facts will be found to 

 confirm the very laws to which at first sight they seem 

 clearly opposed, others will cause us to limit the generality 

 of our previous statements. In some cases the exception 

 may be proved to be no exception ; occasionally it will 

 prove fatal to our previous most confident speculations ; 

 and there are some new phenomena which, without really 

 destroying any of our former theories, open to us wholly 

 new fields of scientific investigation. The study of this 

 subject is especially interesting and important, because, as 

 I have before said (vol. ii. p. 233), no important theory 

 can be built up complete and perfect all at once. When 

 unexplained phenomena present themselves as objections 

 to the theory, it will often demand the utmost judgment 

 and sagacity to assign to them their proper place and 

 force. The acceptation or rejection of a theory will entirely 

 depend upon discriminating the one insuperable contra- 



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