xxii Geneeal Results or the Makeestoun Observations. 
Table 13. — Diurnal Variations of Westerly Declination for different periods deduced from 
Table 12. 
Mak. 
Dec. 
March. 
April. 
May. 
June. 
July. 
Aug. 
Sept. 
Six Months. 
Twelve 
Months. 
Mean 
Time. 
Jan. 
Feb. 
Oct. 
Nov. 
oepi. 10 
Feb. 
J\ia,rcii 
to Aug. 
h. m. 
' 
' 
' 
' 
12 10 
— 1-78 
t AO 
— 1-7.5 
— 1'90 
— 2-16 
-1-97 
- 1-85 
— 1-91 
13 10 
— ] -38 
0 1 A 
1 ^ A 
— l-oy 
— 2-08 
0 AA 
-1-69 
-1-96 
— 1-82 
14 10 
— 1-U5 
0 Ai^ 
— 1-OZ 
1 A'? 
— 1-97 
— 1-40 
-1-22 
-1-88 
— 1.55 
15 10 
— 0-77 
— z-o4 
1 AO 
— 1-78 
— 1-40 
-1-08 
-2-02 
— 1-55 
16 10 
— 0-70 
— 1 •B^t 
000 
— z-oo 
— 2-77 
1 0 ^ 
— 1-37 
- 1-03 
-2-48 
— 1-75 
17 10 
— 0-80 
0 AO 
0 OA 
— 3-45 
— 1-13 
-0-96 
-3-11 
— 2-03 
18 10 
— U-ZD 
0 A /I 
— 4-b7 
0 *70 
A TO 
— U-7Z 
-0-49 
-3-48 
— 1-98 
19 10 
— 0-13 
0 0 
— Z-D.i 
A CO 
— 4-OZ 
0 *70 
— 3-7o 
— 0-77 
-0-45 
-3-64 
— 2-04 
20 10 
+ 0-03 
— 2-65 
0 c e 
— 6-00 
— 2-70 
A C *7 
— 0d7 
-0-27 
-2-97 
— 1-62 
21 10 
+ 0-44 
— 1 '45 
— l-7o 
— 1-1 1 
1 A 0 
+ O-OD 
+ 0-40 
- 1-44 
— 0-52 
22 10 
+ 1-45 
+ 0-69 
+ 0-96 
+ 1-37 
+ 2-40 
+ 1-92 
+ 1-01 
+ 1-46 
23 10 
+ 2-72 
+ 3-7o 
1 0 A 0 
+ 4-27 
+ 4-50 
+ 3-61 
+ 4-00 
+ 3-80 
0 10 
+ 3.47 
+ 6-29 
1 C 0 A 
+ 5-oU 
+ 6-30 
+ 5-7o 
+ 4-61 
+ 6-13 
+ 5-37 
1 10 
+ 3-67 
+ 7-28 
+ 6-53 
+ 6-87 
+ 5-48 
+ 4-57 
+ 6-89 
+ 5-73 
2 10 
+ 2-90 
+ 6-17 
+ 5-97 
+ 5-93 
+ 4-46 
+ 3-68 
+ 6-02 
+ 4-85 
3 10 
+ 1-75 
+ 4-46 
+ 4-45 
+ 4-16 
+ 2-71 
+ 2-23 
+ 4-36 
+ 3-29 
4 10 
+ M1 
+ 2-67 
+ 2-83 
+ 2-52 
+ 1-00 
+ 1-05 
+ 2-67 
+ 1-86 
5 10 
+ 0-26 
+ 0-30 
+ 1-27 
+ 1-09 
+ 0-03 
+ 0-14 
+ 0-89 
+ 0-51 
6 10 
-0-61 
-0-94 
+ 0-47 
-0-34 
- 1-24 
-0-92 
-0-27 
-0-59 
7 10 
- 1-05 
-1-43 
-0-05 
-0-66 
- 1-93 
-1-49 
-0.71 
-MO 
8 10 
-215 
-1-84 
-0-61 
-0-96 
-3-05 
-2-60 
- M4 
-1-87 
9 10 
-2-36 
-2-11 
-0-81 
-1-67 
-2-89 
-2-62 
-1-53 
-2-07 
10 10 
-2-46 
- 1-99 
-1-02 
-1-87 
-3-01 
-2-73 
- 1-63 
-2-18 
-2-36 
- 2-45 
- 1-55 
- 1-79 
-3-01 
-2-68 
- 1.93 
-2-30 
32. The follo\\'ing are the epochs of maximum and minimum westerly declination fi-om Table 13 in apparent 
time : 
Dec. .Jan. Feb. Mar. April. May. June. July. Aug. Sept, Oct. Xov. 
Max. O'l 50™ P.M. I'' 5™ p.m. 1'^ 15™ p.m. 0^ 50°^ p.m. 0^^ 35™ p.m. 
Miu. 8'^ P.M.— ll^^ p.m. 8'^OniA.M. 6*1 30™ A.M. 6b 40m A.M. P.M. lll^P.M. 
33. The form of the diurnal curve is the same for each of the periods of three months ; the westerly declina- 
tion decreases regularly from the maximum till about 8^ p.m., whereas in the cui-ves for the summer months, 
the rate of decrease receives a check about 5'^ or 6'^ p.m. (see Plate I.) No secondary maximum or minimum 
is shewn in these means, but the magnet is nearly stationary for several hours in each case, namely from ^ 
8'' to 11'* p.m. in the months from September to February ; from 8'* p.m. till &^ a.m. in the mean for 3iarch I 
and April, from midnight till 3'* a.m. in May and June ; and from 9'' p.ji. till 3"* a.m. in Jime and July. The j 
magnet is stationary for nearly twelve hours about the 23d of ]N[arch : the transposition of the minimmu of 
westerly declination from before midnight till about 8'' a.ji. takes place very gi-adually in March and April; 
this docs not appear to be the case, howevei-, in the return of the minimiun from 7'' a.^e. to before midnight, 
which occurs about three weeks before the autumnal enuiuox. 
34. When we examine tlic diurnal curve deduced from the observations for tlio wliole year (PlaTo I.), we ob- i 
serve a secondary maximum of westerly declination occurring at 2'' 40™ a.m., nearly equal minima occurring at 
11"^ P.M. and 6'' a.m. ; this secondary maximum is evidently due to the occurrence of the minimum for one- 
half of tl\e year about 10'' p.m., and for tlie other half about 7'' a.m. ; The mean for the year therefore does not 
represent, as far as these results are concerned, a real phenomenon ; it is a combination of two distinct rosidt*. 
35. The previous conclusions are obtained from the moans of all the regular daily observations : no observa- 
tion has been rejected how ever niucli atl'ected by magnetic irregularity ; we have still to inquire therefore to 
what extent irregular causes change the diurnal variation. A itiethod has been already proposed and employed 
