4 1 On the Magnetic Injiuence of the Lunar Spectrum. 



ment, and that the prism was so held, that the blue rays of 

 the spectrum were nearest the eastern horizon. 



16. After this cessation of motion, the needle with its head 

 directed towards the true north pole of the earth, soon began 

 to move laterally as before ; but although it went through the 

 same varied and peculiar changes of position as it did pre- 

 viously, but more slowly, it exhibited a short cessation of mo- 

 tion when it was parallel to the terrestrial equator, which was 

 not the case when its point deflected from the meridian in the 

 first instance, and its darting equatorial motion was less rapid 

 than before ; but it underwent the same extent of bodily 

 movement on the surface of the water, as to distance, before 

 it was again parallel to the true meridian of the earth. When 

 it attained that position, and its point was its north pole, there 

 is^as no pause, as was the case when its head was so situated, 

 for the subsequent lateral movement immediately followed. 



17. After it had gone through a third series of these varied 

 changes of position, and its head was again its north pole, the 

 corresponding cessation of motion occurred. The prism was 

 removed for a iev,- seconds. Upon its being replaced, the head 

 of the needle deflected from the meridian towards the voestt 

 and the direction of the rotation was reversed. 



18. Finally, when the prism was removed permanently, the 

 needle soon arranged itself in the magnetic meridian with that 

 end pointing towards the north, which was on that side of the 

 equator, when the prismatic influence ceased to operate. But 

 the change of poles was not permanent, as had been found to 

 be the case when the needle was acted upon by the solar 

 spectrum : for its point gradually came round to the north if 

 its head had been at first attracted to that position, or been 

 left there when the prism was removed. 



19. These observations appear to corroborate a new physi- 

 cal theory, which has been graduall}' suggested by meditation 

 upon the leading phaenomena of electrical inductioji, but as 

 the outlines of my general hypothesis do not coincide with the 

 published opinions of several natural philosophers, for whom 

 I entertain sincere respect, I abstain from offering them to 

 the public until the magnetic influence of the moon has been 

 made the subject of their investigation. My present object 

 is to direct their attention to the above observations, and to 

 invite them both to repeat my experiments (which are un- 

 doubtedly liable to error) and to attempt the solution of the 

 great magnetic problem involved in this manifestation of a 

 lunar influence upon the weak but constant polarity of a 



