100 
tion from S. 69° 36' W. to N. 69° 36' E. Now, this direction 
is almost exactly that of a perpendicular to the magnetic 
meridian. Referring to the Greenwich Magnetical Observa- 
tions, we find that the magnetic declination in the years 
1859-1865 
was as follows 
1859 .. 
21 23-5 W. 
1863 .... 
.... 20 46*0 W. 
1860 .. 
21 14*3 „ 
1864 .... 
.... 20 38*0 „ 
1861 .. 
21 5-4 „ 
1865 .... 
.... 20 35-0 „ 
1862 .. 
20 52*0 „ 
The mean for the seven years is 20° 56*3' W., a perpen- 
dicular to which is S. 69° 3*7' W. to N. 69° 3*7' E., thus 
differing only 32*3' from the above determination. This 
close relation to the direction of the magnetic meridian, 
taken in connection with the points of agreement between 
the phases of the two classes of phenomena already adverted 
to, seems to establish beyond doubt the fact that the force 
which produces the diurnal inequality in the direction and 
velocity of the wind, and the earth’s magnetic force, are in 
some way intimately connected with and dependent upon 
each other. 
It has, I believe, been generally supposed that the mean 
position of the magnetic needle for the 24 hours of each day 
indicates the direction of the true magnetic meridian, or is 
that in which the needle is subject to the least amount of 
disturbing force; and that its diurnal oscillations are due to 
two forces acting alternately in opposite directions, or to 
one force, the acting centre of which changes its position so 
that during part of the 24 hours it is on one side of the 
magnetic meridian, and during the other part on the oppo- 
site side; but the results of this discussion of the Oxford 
Anemograph Observations seem to show that the greatest 
easterly deflection of the needle should be taken as the 
direction of the true magnetic meridian; and that the daily 
oscillations are due to one disturbing force only which, 
when in operation, acts always in the same direction. 
