246 M. KreiPs 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.— a West. 
20 0 
22 30 
1 0 
4 30 
7 30 
11 0 
+ 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 presenting 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 
