and Directive Force of the Magnetic Needle. 39 
at noon sei at 6 a.m., and greater at 6 p.m: than at noon, unless 
the currents in action at noon should pass off entirely during the 
afternoon, The effect of the residual currents at noon being ap- 
ng 
some unknown law, would be approximately proportional to the 
difference between the ecliptic currents at G a.m. and at noon, In 
the play of the two tendencies just mentioned I conceive that we 
have the general explanation of the diurnal variations was the ver- 
- tical force. , 
TABLE IV. 
Mean anal Variation of the Vertical Force in each Month of Md 
ronto; derived from Hourly Observations in the Years 1843 to 
| Astron, 9 Tr... “ua A AD r T. - A | ~~ fine 7 A T. to Ie ct, to 
P aacolecns a i y g i Nov, © san ine.| Mar. inc. . Sen 
00} -00 | -00} “00 | -00 | -00 | -00 | -00 | “00 00 eo “00 | 00 | 
On 7 aa 006 | 086 13 | 015 | 
1 011 011 024 ' 017 | O19 | 
ree, 017 017 ? | 5 030 028 | 025 | 
ei 99 ~ 34! 046) 0560: | 026 | 029 | 
4 0} 052) 0 0 26 | 081 | 
| | 027 | 032 | 
6 | 027 | 031 | 
q 02 | OBI \ 
8 027 | 028 | 
pic Nee Ook 023 | 023 | 
2. 021 | 618 | 
lI 014 | 012 | 
12 008 | L06 
13 006 | 062 | 
1 004. | 000 ; 
15 004 | OO1 | 
16 000 | 001 | 
17 * 0 oo2 | 005 | 
18 005 | 010 
19 008 } O11 
20 013 | 013 
21 ‘009 908 | 010 
22 (01.0002 0034011 009 4 01 }024/020}007/012) 013 | 007 | 00% 
| 23 0031002 00 002 ah 009 001/ 014| 024 028/019!009/013/ 014 | 008 | 009 
“The diurnal variation of the vertical force at Toronto in both 
pi t. e., from April to September inclusive, and from October 
0 March inclusive, i is a double. penaryenon having two maxima 
two minima. The principal maximum takes place two hours 
earlier from April to September than rat ay iets to March, viz, 
at 5% from April to September, and at 7» from October to March. 
From this maximum the diminution is progressive to the princi- 
pal minimum, which also occurs earlier deo April to September 
than froma October to March; 7 ¢., between 14" and 155 (2 a.m. 
and 3 a. M.) from April to September ; j aah at 16" (4 4. M.) from 
October to March. The see ry minimum is at 22h (10 a. m.) 
in both seasons. The range of the diurnal Variation is sii 
MEET G RE IO runt 
