Masterpieces of Science 



they were regulated, and bv which their period 

 might perhaps itself be rendered variable, were 

 to be examined; and finally their relation to 

 other natural laws was to be sought after. That 

 science should set herself to an inquiry so delicate 

 and so difficult, in a spirit so exacting, was no- 

 thing unusual. It is thus that all the great dis- 

 coveries of our age have been effected. But it is 

 well that the reader should recognize the careful 

 scrutiny to which natural phenomena have been 

 subjected before the great laws we have to 

 consider were made known. It is thought by 

 many, who have not been at the pains to examine 

 what science is really doing in our day, that the 

 wonders she presents to men's contemplation, 

 the startling revelations which are being made 

 from day to day, are merely dreams and fancies 

 which replace indeed the dreams and fancies of 

 old times, but have no worthier claims on our 

 belief. Those who carefully examine the history 

 of science will be forced to adopt a very different 

 opinion. 



The minute vibrations of the magnetic needle, 

 thus carefully watched day after day, month 

 after month, year after year were found to 

 exhibit a yet more minute oscillatory change. 

 They waxed and waned within narrow limits of 

 variation, but yet in a manner there was no 

 mistaking. The period of this oscillatory change 

 was not to be determined, however, by the 

 observations of a few years. Between the time 

 when the diurnal vibration was least until it had 

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