244 
Abstracts of Makerstoun Observations, 1843. 
Each of the four months gives nearly the same result. In the means of the months about the summer 
solstice, there are two maxima and two minima, the diurnal curve is also double : — 
The minimum (as far as it can be deduced from the 9 observations), occurs at Noon, Makerstoun mean time. 
The maximum occurs about 6 h 10™ p.m., 
A minimum occurs between 9 h p.m. and 5 h a.m., 
A secondary maximum occurs about 8 h a.m., • 
Whether the principal maximum occurs near noon or near midnight cannot be determined from the obser- 
vations, but an examination of the monthly means will shew that the noon minimum becomes more marked from 
January till June, and then becomes less so till December. 
The result for the whole year is exactly that for the equinoctial months. 
As the above results agree on the whole with those for the year 1844,* it may be permissable to con- 
clude, that, — 
1st, The diurnal curve is single in winter, unequally double at the equinoxes, and nearly equally double 
at midsummer. 
2d, The minimum near noon occurs at the same hour in the equinoctial and summer months ; the morning 
maximum occurs nearer noon in the equinoctial than in the summer months ; the principal or evening maximum 
occurs nearly at the same hour in the winter and summer months, and farther from noon than in the equinoctial 
months. 
In order to determine the period of the principal minimum, the observations made at 0 m on the term-days 
of 1842 and 1843 have been used. The observations in 1842 were corrected by various temperature coeffi- 
cients, depending on the method of deflections, the means in the following table were obtained after farther cor- 
rections had been applied for the differences of the first coefficients from that obtained by comparisons of the 
daily observations. The means in the following table are deduced from the term observations at 0 m in 1842 
thus corrected, and, from the term observations in 1843, as corrected in this volume. The winter solstice includes 
the months of November, December, January, and February, 1842 and 1843 ; the equinoxes, the months of 
March, April, September, and October, 1842 and 1843 ; and the summer solstice, the months of May, June, 
July, and August, 1842 and 1843. 
TABLE XIX. — Diurnal Variations of the Vertical Component of Magnetic Force, deduced from the 
Observations at 0 m on the Term-Days of 1842 and 1843, the whole Vertical Component being 
Unity. 
Hour. 
Winter 
Solstice. 
Equinoxes. 
Summer 
Solstice. 
1842. 
1843. 
Mean. 
Hour. 
Winter 
Solstice. 
Equinoxes. 
Summer 
Solstice. 
1842. 
1843. 
Mean. 
0-00 
0-00 
0-00 
0-00 
0-00 
0-00 
0-00 
0-00 
0-00 
O'OO 
0-00 
0-00 
10 
0250 
0572 
0299 
0492 
02S1 
0357 
22 
0141 
0589 
0351 
0510 
023S 
0344 
1 1 
0190 
0532 
0256 
0410 
0267 
0309 
23 
0151 
0590 
029S 
047S 
0240 
0329 
12 
0080 
0420 
0153 
0292 
0170 
0201 
0 
0184 
0552 
0241 
0460 
021S 
0309 
13 
0000 
0083 
0029 
0000 
0101 
0021 
1 
0220 
0517 
0233 
047S 
0194 
0306 
14 
0051 
0000 
0000 
0008 
0052 
0000 
2 
0229 
0510 
028S 
0500 
0211 
0326 
If) 
0078 
0064 
0036 
0144 
0000 
0042 
3 
0225 
0556 
0359 
0547 
023S 
0363 
Hi 
0077 
0099 
0073 
0186 
0007 
0007 
4 
0251 
0671 
03S2 
0622 
0274 
0418 
17 
0063 
017S 
0189 
0264 
0049 
0126 
5 
024S 
0729 
0401 
0632 
0313 
0443 
18 
0058 
0312 
0262 
0315 
0103 
0194 
6 
0228 
07S3 
0425 
063S 
0345 
0462 
19 
00S3 
0420 
0341 
0447 
0142 
0265 
7 
0227 
07SS 
0441 
0661 
0336 
0169 
20 
0095 
0530 
0336 
0483 
0184 
0303 
8 
0197 
0707 
0473 
0032 
0313 
0443 
21 
0 1 29 
0587 
0317 
0492 
0242 
0337 
9 
0194 
0604 
044S 
0563 
0293 
0399 
In the mean for all the periods, the principal minimum occurs at midnight, or l h a.m. In the mean for 
botli years, the principal minimum occurs at l h a.m. The principal minimum perhaps occurs nearer noon in 
* Transactions of the Royal Society of Edinburgh, Vol. XVI., p. 137. 
