31 



HO doubt, the friends, and perhaps the relatives of the observer, have 

 presumed to ridicule his devotion to what seemed to them a trivial 

 pursuit ; but the result of all this labour was the discovery of what 

 had escaped the attention of all astronomers for two hundred years, 

 at least had been before only very faintly suspected, viz. that the spots 

 on the sun's disk pass through the phases of maximum and minimum 

 frequency in a period of about ten years. But, strange to say, it was 

 then discovered, and first announced in our Transactions by General 

 Sabine the discoverer, that the decennial magnetic period coincides, 

 both in its duration and in its epochs of maximum and minimum, with 

 the decennial period observed by Schwabe in the solar spots ; that is, 

 the period of maximum variation with that of the maximum fre- 

 quency of spots, and so vice versa the minimum. Hence it is clear that 

 the sun exercises some influence on the earth's magnetism dependent 

 on the existing state of its own luminous atmosphere. Surely this is 

 another remarkable instance that fact is often more strange than fiction. 

 How little could the secluded observer, watching the quiverings of the 

 needle in the remote regions of Australia, or on the shores of the 

 Polar Sea, dream either that his labours would derive additional 

 interest from the unconscious cooperation of a German astronomer, 

 or that he was himself engaged in watching vibrations which were 

 oscillating in harmony with the motions of a gaseous substance ninety- 

 five millions of miles away ! This is again another example added to 

 the many other illustrations of the same truth, that scientific re- 

 searches, if skilfully and perseveringly continued, often lead to most 

 valuable results, which could not have been anticipated a priori ; 

 and this should surely be as great an incentive to toil as it is a glorious 

 reward of discovery. 



But this is not all : it has been found also that our less obtrusive 

 satellite, that the mild influence of the moon affects the magnetic 

 needle ; the declination, the inclination, and the magnetic force, all 

 undergo a small variation, dependent on the lunar hour angle. A 

 delicately suspended magnet is truly the most submissive of all 

 slaves, affected by the sun, and the moon, and the earth, and the 

 sport of every electric or magnetic current that approaches it. 



" Whate'er the line 



Which one possessed, nor pause nor quiet knew 



The sure associate, ere, with trembling speed, 



He found its path, and fixed unerring there." 



