246 M. Kreil's Magnetic Observations. 



as we have seen in (7.) is different at different hours of the 

 day. But in a longer series of observations, on account of 

 the periodicity of the last named alteration, the effect of a 

 constant though much weaker cause acting according to quite 

 a different law must be traceable, as the result has shown. 

 The following are the differences at the different hours of the 

 day between the declinations found with moon east and moon 

 west. 



Hours. 



C East.— C West. 



20 



22 30 



1 



4 30 



7 30 



11 



+ 10"- 8 

 + 27 -5 

 + 9-1 

 + 25 -9 

 + 8-3 

 + 8-0 



Mean 



+ 14 -9 



It is true that these numbers are not yet corrected for the 

 secular decrease of the declination, but it does not appear to 

 have been great enough to affect the result essentially. In 

 the year 1836 the observations were not made exactly at the 

 same hours, and cannot therefore be employed for determi- 

 ning the secular alteration, but from 1837 to 1838 it was 59"*8, 

 which would give a correction of 2"*5. This if doubled 

 would not alter any of the signs in the above table. We 

 conclude hence, that in this country the declination is always 

 greater when the moon is east of the magnetic meridian, and 

 less when it is west. 



16. All the results which we have derived from our obser- 

 vations in reference to the effects produced by the moon agree 

 in pi'esenting her as a body exercising magnetic influence, 

 and in which the prevailing magnetism on the hemisphere 

 turned towards the earth attracts that pole of our needles 

 which is turned towards the south, and increases the magnetic 

 intensity of our hemisphere. 



The observations of perturbations have manifested the 

 following facts : 



17. Great disturbances frequently occur on the same day,. 

 or nearly on the same day, in different years. Thus the 

 greatest disturbances which took place in the year 1836 were 

 on the 22nd and 23rd of April, and on the 18th of October, 

 and both these were repeated on the same days in 1837. In 

 1838 several of the disturbances took place a few days later 



