ATMOSPHERIC MAGNETISM — ANNUAL VARIATION. 
73 
Hobarton. Lat 42° 52'-5 S. 
Toronto. Lat. 43° 39'‘35 N. 
January . 
. . . 11-66 .... 
.... 6-51 
February 
. . . 11-80 . . . . 
.... 6-40 
March 
. . . 9-50 .... 
.... 8-50 
April . . 
. . . 7'26 .... 
.... 9-52 
May . . 
. . . 4-56 .... 
.... 10-34 
June . . 
. . . 3-70 Winter. . 
.... 11-99 
July . . 
. . . 4-61 .... 
August . 
. . . 5-89 .... 
.... 12-68 
September 
. . . 8-24 .... 
.... 9-72 
October . 
. . . 11-01 . . . . 
November 
. . . 12-05 Summer . 
.... 5-75 
December 
. . . 11-81 . . . . 
The two stations are in latitudes differing only 47' from each other ; and the extreme 
difference of the atmospheric effect between summer and winter differs as little, being 
at one, Hobarton, which has the highest latitude, 8'’35, and at Toronto 8'‘23. 
2949. According to Dove, the northern hemisphere is warmer in July than the 
southern hemisphere by 17°'4 Fahr., and colder in winter by only 10°‘7 ; the numbers 
being as follows : — 
July. 
0 
Northern hemisphere 71 ’O' 
Southern hemisphere 53-6, 
^62°-3 the whole globe. 
January. Northern hemisphere 48'8" 
Southern hemisphere 59’5, 
>54°- 15 the whole globe. 
The mean for the whole year is 59°'9 for the northern hemisphere, and 56°'5 for the 
southern. Therefore, as Dove further shows, the whole earth is in July, when the 
sun is shining over the terraqueous parts, 8° higher in temperature than in January, 
when it is over the watery regions : and from the influence of the same cause, the 
mean of the southern hemisphere is 3°’4 below the mean of the northern half of the 
globe. The difference between January and July is for the northern hemisphere 
22°‘2, and for the southern only 5°'9. These differences are so peculiar in their 
arrangement and so large in amount, that they must have an effect upon the distri- 
bution of the magnetic forces of the earth, but the data are not yet sufficient to 
enable one to trace the results. Sabine indicates a probability from his analysis of 
observations, that the sum of the earth’s magnetic force is increased in intensity 
when the sun is in the southern signs, i. e. in our winter (2891.). I should have ex- 
pected from theory that such results would have been the case, at least in those parts 
where the dip was not very great ; because a colder atmosphere ought to conduct the 
lines of magnetic force better, and therefore the systems round the earth ought at 
such a time to condense, as it were, in the cooler parts. It would be doubtful, how- 
ever, whether the needle would show this difference, because the lines of power would 
MDCCCLI. L 
