XXXil INTRODUCTION TO THE MAKERSTOUN OBSERVATIONS, 1843. 
turned through 69° 44’, reading A 287° 44’, the scale reading being 148. The 
westerly declination during adjustment was 25° 28’. 
November 8# 21" 20™. The bifilar magnet was removed in order to determine its 
temperature correction ; the brass weight being substituted, the arms of the torsion 
circle were turned from A 287° 44/ to A 357° 30’, when the collimator scale read 
157-5, or 9°5 scale divisions greater than on April 28, the westerly declination being 
25° 20’. As it is necessary to determine the changes of horizontal force during the 
observations for the temperature correction, the magnet used for deflections in ob- 
servations of absolute horizontal intensity was substituted. The moment of this 
bar was found too great for grooved wheel No. 8, previously in use (Introduction, 
1841-2. 30.), wheel No. 9 was substituted, whose diameter = 0-459 inch; as the 
diameter of wheel No. 8 = 0-409 inch, and the value of one division of the micro- 
meter-headed screw = 0:0005194 inch, the wires were rendered parallel by turning 
the micrometer head through 96 divisions. 
The brass weight being suspended, the scale reading was 128:5 
Me MALE «00. ccasesonescccnscenvecsaresenpescvnvasersneseapsearoe 126-0 
The weight being suspended, the arms of the torsion circle were turned through 90°, 
when it read, vernier A 178° 0’, B 358° 0’; the collimator was then turned by its 
independent motion till the scale reading was 143; the magnet was suspended, and 
the scale reading was found 142 when the arms of the torsion circle were turned 
through 55° 17'°5, the circle reading A 122° 41-5, B 302° 43’. 
November 104 6". The temperature experiments having been made, the de- 
flecting bar in the bifilar magnetometer was removed, and the arms of the torsion 
circle were turned from B 302° 43’ to B 358° nearly, when the scale reading was 143, 
as in the previous adjustment. Wheel No. 9 was removed, and No. 8 substituted, 
the micrometer head being turned backwards through 96 divisions. 
» The bifilar magnet being suspended, the scale reading was 93 
The brass weight .......cssssressssscascestneceneanseneceeasesescens 96 
the arms of the torsion circle were turned through 90°, when the reading was B 
358° 35’; the collimator was turned by its independent motion till the scale reading 
was 172-4, the magnet was inserted and the arms of the torsion circle turned through 
68° 18’, when the torsion circle reading was B 290° 17’, and the scale reading 173°. 
The bifilar thermometer 42-4, and the absolute westerly declination 25° 18’. 
39. The following are the values of v, of k = a cot v, and of q’ a with the 
periods to which they apply in 1843. 
