IN THE MEAN EFFECTS OF THE LARGER MAGNETIC DISTURBANCES. 369 
are they always complementary to each other. Thus, from 1 p.m. to 5 p.m. both 
classes of the Declination-disturbances are considerably below the average, and from 
1 A.M. to 5 A.M. both classes, with a slight exception, are above the average ; whilst 
from 6 P.M. to 1 1 p.m. easterly disturbances greatly exceed, and westerly fall greatly 
short of the average ; and from 6 a.m. to 11 a.m. westerly exceed, and easterly fall 
short of the average. In the Inclination and Total Force the complementary character 
of the opposite affections of each element is more extensively manifested ; thus the 
disturbances which increase the Inclination are below the average from about noon 
and the early hours after noon, when those which decrease it are above the average ; 
and are below the average from about midnight and the early hours after midnight, 
when those which increase the same element are above the average. In the Total 
Force, from 1 a.m. to 8 a.m. the disturbances which increase the force are greatly above, 
as those which decrease the force are greatly below the average ; a contrast which is 
reversed from 1 a.m. to 8 a.m., the disturbances which decrease the force being then 
greatly above, whilst those which increase it are greatly below the average. In 
neither of the two elements however does the complementary character exclusively 
prevail. It may be remarked, that in all the instances which have been thus brought 
into view, touching successively the diurnal variations of the disturbances of each of 
the three elements, the parallel cases which have been cited, whether of identity or 
of contrast, fall without exception on homonymous hours; a circumstance which 
affords additional evidence of the systematic character of the affections of which we 
are treating. 
There does not appear to be any uniform contemporaneous connexion between the 
prevalence of either easterly or westerly Declination-disturbances and of those which 
either increase or decrease the Inclination or the Total Force. Thus, for example, the 
hours at which the disturbances which increase the Total Force are most notably above 
the average are from 1 p.m. to 9 p.m. ; whilst we find that for half that period, or from 
1 P.M. to 5 P.M., the Declination-disturbances are characterized by a very low propor- 
tion of easterly disturbances, and for the other half of the period, or from 6 p.m. to 
9 P.M., by a very high proportion of easterly disturbances ; and without multiplying 
instances of dissimilarity, it may be remarked generally, that the more the six classes 
of disturbances are examined and compared with each other, the less reason does 
there appear to conclude that there is any uniform interaccompaniment of the varia- 
tions of different elements. 
As the instrument by which the variations of the Declination are observed is more 
simple in construction than those required for the variations of the Inclination and 
Total Force, and the disturbances of the Declination are therefore more easily observed 
and more generally known, a somewhat disproportionate considemtion has been fi’e- 
quently given to them in the discussion of these phenomena, which it may be 
desirable briefly to remark upon. Thus the knowledge of the magnetic disturbances 
having been ehiefly drawn from those of the Declination, it has been very generally 
