OF THE EARTH’S MAGNETISM. 555 
sisting of only four observations daily) to determine in this way the error, if any, 
in returning the arms of torsion circle 1842, July 2. A comparison of the monthly 
means with those elsewhere would render it probable, however, that the mean at 
Makerstoun for July is too great compared with that for June ; but no correction 
has been applied. In 1843 the series of observations was still incomplete, but as it 
consisted of nine daily observations, the means for the same hours for the periods 
in question were taken for places near the same meridian; though, owing to the 
difference of the diurnal law of disturbance at different places, the corrections 
obtained cannot be considered so satisfactory as if the whole day had been 
employed. 
108. 1843, April 23.—Adjustment at Makerstoun. The following are the mean 
forces in ten-thousandths* of the whole horizontal force at each place :— 
TABLE XXXIV. 
a 

















Days. ar Change. Jee Change. || Brussels. | Change. ||Hobarton.| Change. 
April 24, 25, 26, 28. Adjust. || 27°27 21:27 21:98 39°68 
Lys) CNS Sas ee 28°60 | +1°33 || 21:35 | 40-08 || 19-67 | —2°31 | 38°73 | —0-95 
<n Jp ee 28°89 | +1°62 || 22:26 | 40:99 }| 22°39 | +041 
Mean Change,-. . . . +1:47 +0°538 — 0:95 —~0:95 
By St Helena, the values at Makerstoun, after April 28, require the correction —0:94 
;, Brussels, nee ea sie — 2°42 
», Hobarton, nen Bae ape — 2-42 
The correction — 1:00 was adopted before the results at Brussels and Hobarton 
were obtained. This correction is probably too little, though, since the correction 
for temperature at Brussels was only approximate, and the difference of meridians 
at Hobarton is so great, the results by the two latter places should perhaps have 
a less value than the result from St Helena. 
109. 1843, May 6.—Torsion circle arms turned and returned. 
By the mean of the three places (see Table XXXYV.) the values at Makerstoun, 
after turning the arms of the torsion circle, require the correction — 7:95. The 
correction adopted after May 6 was — 8:00. A more extended comparison, in- 
cluding more days, and the observations at Hobarton, would render it probable 
that this correction is also slightly too little. 
* In this Appendix the units are always ten-thousandths of the force, unless when sc div. 
(scale divisions) is affixed. 
VOL. XXII. PART III. TD 
