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" 10™ p.m., sve:aaelossiers enacted 
A minimum occurs between 9" p.m. and bh AM., 
A secondary maximum occurs about 8" a.m., ste tee tee nee eee aee ene 
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 oceurs 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™ 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™ in 1842 
thus corrected, and, from the term observations in 18438, 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™ on the Term-Days of 1842 and 1843, the whole Vertical Component being 
Unity. 
Winter Equinoxes. Summer 1842. 5 é . || Winter Bquinoxes. Summer | jg49. | 1943, 
Solstice. Solstice, 
Solstice. Solstice. 
0-00 0:00 0-00 0-00 : . 0-00 0-00 0-00 
0250 0572 0299 0492 0141 0589 0351 
0190 0532 0256 | 0410 B 0151 0590 0298 
0080 0420 0153 0292 0184 0552 0241 
0000 0083 0029 | 0000 0220 0517 0233 
0051 0000 0000 0008 0229 0510 0288 
0078 0064 0036 | 0144 0225 0556 0359 
0077 0099 0073 0186 0251 0671 0382 
0063 0178 0189 | 0264 0248 0729 0401 
0058 0312 0262 0345 0228 0783 0425 
0083 0420 0341 0447 0227 0788 0441 
0095 0530 0336 | 0483 0197 0707 0473 
0129 0587 0347 0492 0194 0604 0448 
COANAMTMKRWNHS 
In the mean for all the periods, the principal minimum occurs at midnight, or 1" a.m. In the mean for 
both years, the principal minimum occurs at 1" a.m. The principal minimum perhaps occurs nearer noon in 
* Transactions of the Royal Society of Kdinburgh, Vol. XVI., p. 187. 
