62 DR. FARADAY’S EXPERIMENTAL RESEARCHES IN ELECTRICITY. (SERIES XXVI.) 
The mean declination is 22° 51' 18" W., and the mean inclination is 69° N. As 
it is the upper end of the dipping-needle which we have to consider for the purpose 
of a ready comparison with the sun’s observed day action (2906.), I will describe that 
part of its course and place for Greenwich time which concerns us now. Moving 
westward before 19^ and 20\ it then returns towards the east, and in six hours, or by 
l'’ or 2'', has completed the great sun swing, after which it returns west, following the 
luminary. The vertical force is given as greatest between 3 and 4 o’clock, and least 
between 1 1 and 13 o’clock. The south end of the needle therefore is more upright at 
the former time and less at the latter ; and as the latter occurs during the prolonged 
return part of the journey from east to west, including the night hours, so we perceive 
that the upper end of the needle performs its daily journey in an irregular closed 
curve, which the ellipse for Toronto, fig. 13 (2909.), may generally represent; it 
passes from east to west slowly during the night hours, approaching the equator at 
the same time, and then it returns from west to east with far greater rapidity, per- 
forming this part of its journey at a greater distance from the equator and nearer to 
the pole. 
2912. PFashington, U.S. — Latitude 38° 54' N. ; longitude 77" 2' W. ; the mean 
declination 1° 25' W. ; the mean dip 71° 20' N. The south or upper end of the 
needle is in the morning at extreme west, about 20 to 22 o’clock, and at extreme east 
about 2 o’clock ; it then returns slowly west, with the night action as in former cases, 
regaining extreme west at 20 to 22 o’clock. This is exactly the same movement for 
declination, in relation to the place of the sun, as for the former localities. I have 
not the variation of the dip, but theory would lead one to conclude thnt it is greatest 
between 22 and 2 o’clock, and least in the evening and night time. The total amount 
of declination variation is greatest in summer, as before, being 9'‘87 in July and only 
4' in December. The greatest difference in the earth’s temperature is also in July, 
being then nearly 20° Fahr., whereas in December and January it is only 10° Fahr. 
The shortest period between the extreme temperature, including therefore the quickest 
change of temperature, is from 16 or 18 to 2 o’clock, and consequently includes noon. 
All these conditions combine to produce the greatest magnetic action, and it is in the 
direction pointed out by the hypothesis. 
2913. Lahe Athabasca. — Latitude 58° 41' N. ; longitude 111° 18' W. of Green- 
wich ; mean declination 28° E. The observations are only for five months, but as 
the position is in a high latitude and may be important for future considerations, I 
give the results here. The extreme western position of the upper end of the needle 
is about 17 or 18 o’clock, and its extreme eastern position about 1 or 2 o’clock; so 
that, as far as declination is concerned, the action of the sun and atmosphere is as in 
former cases. The amount of declination variation is very great, being in October 
2l''32; in November 10'’8; in December 9'‘78; in January 16'‘29, and in February 
J4'-87. 
2914. Fort Simpson. — Latitude 61°52'N. ; longitude 121° 30' W. of Greenwich; 
