IN THE LARGER MAGNETIC DISTURBANCES. 
173 
Separating the whole body of disturbances at St. Helena and the Cape of Good 
Hope into their easterly and westerly components, it is thus found that the law of the 
hourly disturbance has the same general characteristic feature when viewed separately 
in either direction as when together, viz. the preponderance of disturbances during 
the day over those during the night. This would be anticipated from the large 
excess of the total daily disturbances ; but the fact is interesting as evidencing a law 
different from that by which the disturbances both at Toronto and Hobarton are 
regulated. When the disturbances at these places were separated into their easterly 
and westerly components, it was found that for the purpose of comparison they 
should be arranged into two classes, viz. the easterly disturbances at Toronto and 
the westerly at Hobarton into one class, and the westerly disturbances at Toronto 
and the easterly at Hobarton into another ; the results are elsewhere published in 
detail*, but it may be convenient here to repeat the general conclusion, viz. as 
respects the first class (easterly at Toronto and westerly at Hobarton), it was found 
that, at Toronto, the nightly disturbances were to the daily as 2‘0 to 1 in number and 
as 2-8 to 1 in value. At Hobarton the nightly disturbances were to the daily as 1-6 
to 1 in number and as 2'4 to 1 in value, the disturbance being greater at both places 
at an^ hour of the night than at an^ hour of the day. Respecting the second class 
(westerly at Toronto and easterly at Hobarton), the period of twenty-four hours 
required to be otherwise divided. At Toronto (westerly) the numbers and values 
were uniformly less at every hour from noon to midnight than at any hour from 
midnight to noon. At Hobarton (easterly) the numbers and values were greater at 
any hour from 6 a.m. to 5 p.m. than at any hour from 6 p.m. to 5 a.m., or the easterly 
day distui'bance greater than the easterly night disturbance. In this last we recog- 
nize a similarity in the law to that in both directions combined, or either separately, 
at the Cape and St. Helena ; and although we found that the total disturbance at 
Hobarton showed a preponderance during the night to that during the day, it is 
evident this was caused by the westerly maxima having overridden and masked the 
easterly maxima. 
It has already been shown, as the result of the separation of the disturbances at 
St. Helena and the Cape into easterly and westerly movements, that in each separate 
instance, as in both combined, there is the same general law, viz. the maxima of 
frequency and amount occurring in the day hours and the minima in the night hours. 
When closely followed out, however, the law of easterly and westerly disturbances 
presents some differences. Table IX. contains the total amounts of easterly and of 
westerly disturbances observed during all the years in which the observations under 
discussion were made, in frequency and value, at the several hours of their occurrence 
at St. Helena and the Cape of Good Hope. 
* Philosophical Transactioas for 1852, p. 103. 
2 A 
MDCCCLIII. 
