ATMOSPHERIC MAGNETISM— CAPE OP GOOD HOPE. 
105 
3032. I am inclined to refer much of this precession of the warm region at Toronto 
to the geographiciil distribution of land and water there. The Atlantic is on the 
east and the continent of America on the west of the station, and as Dove’s charts 
and results intimate, the temperature may rise higher and sooner over the land than 
over the water, and so throw the warm region in respect of Toronto in advance of the 
time or of the sun. In the case of Hobarton the arrangement is different ; and, in fact, 
what land there is is between the advancing sun and the station, and would tend to 
hold the warm air region back, and tend to cause its time to coincide with that of 
the sun. Even the greater difference in summer than in winter at Toronto appears 
to be explicable in the same manner, by reference to the relative position of the sun 
at the two seasons to the land and water arrangement. 
3033. Though the temperature on the earth’s surface is a very uncertain indication 
of that above (2937-), yet as far as it goes it harmonizes with this view. The maxi- 
mum temperature occurs sooner after midday at Hobarton than at Toronto; in the 
former place it is at 2 o’clock and very regular, and the minimum at 16-19 o’clock, 
being earlier in summer and later in winter. At Toronto the maxima are from 2 to 4 
o’clock, and the minima at 16-18 o’clock. The maxima are later in summer than 
in winter; the minima are as at Hobarton, being later in winter than in summer. 
The mean temperature is lower at Toronto than at Hobarton, being as 44°'48 and 
53°'48 ; the range of variation is also greater, being at Toronto 43° and for Hobarton 
only 18°. 
3034. It is probable that effects of retardation and acceleration, in respect of the 
passage of the local part of the warm region for a given place, may occur in many 
parts of the globe, and these will require to be ascertained for every locality and for 
the different seasons there. A place having the reverse position of Toronto would 
have a reversed or retarded effect ; and hence it might happen that needles in the 
same latitude might be affected at very different local times, and yet all be regularly 
affected every twenty-four hours. The region would in that time make its diurnal 
revolution, but vary in the velocity of its different parts at different periods of its 
journey, and that in a different degree and order for different latitudes, and for dif- 
ferent parts of the same parallel of latitude. Even the time during which the effect 
(as for instance the sun-swing) continued would probably be altered ; one place 
holding the influence longer and another dismissing it sooner, analogous to two con- 
ditions of stable and unstable equilibrium. 
3035. Cape of Good Hope *. — This station is in longitude 18° 33' east and latitude 
33° 56' south. The mean declination is 29° west and the dip 53° 15' south. The 
amount of dip, combined with the position of the place, gives a magnetic equator, 
which passes nearly through the astronomical poles, and so the sun’s path in every 
part of the year intersects it almost at right angles and at the same hour, namely, 
about 20' past 7 o’clock in the morning and evening, or at 19^ 20' and 7^ 20'. But 
* See Tables, pp. 117, 118, and curves of variation, Plate Ib 
MDCCCLI. 
P 
