xlii INTRODUCTION TO THE MAKERSTOUN OBSERVATIONS, 1845 anp 1846. 
measure, its logarithmic tangent being given, column 12, Table 5; and the latter in’ 
micrometer divisions, reduced to the temperature of the deflecting bar during hori- 
zontal deflections ; @ is the magnetic dip, the adopted value being 71° 20’. The 
temperature coefficient of the deflecting bar = 0-000285. 
The mean of all the values of &, 13th column, Table 5 = 0:00000994. 
60. When the vertical deflections of the balance needle made July 14 and 2¢ 
1846, are compared by the previous method, with the horizontal deflections of the 
same needle, given Table 6, allowance being made for the loss of magnetism of the 
deflecting bar between July 1846 and January 1848, & is found = 0-00001025. 
The adopted value of & for the balance magnet=0-0000100 
This value of one micrometer division in parts of the whole vertical component 
may be considered applicable to all the observations of the balance magnet since 
1841: it has been used in the abstracts of results for the present volume. 
61. The balance needle was deflected July 1 and 2, 1846, for the purpose of de- 
termining the value of k, it was readjusted on July 24. 
As the readings of the micrometer had become previously too much negative, 
the horizontal screw was turned in a little, the following comparisons of observations 
before and after the adjustment were made for the purpose of BUGGED the two 
series. 
Mic. Div. 
Mean balance reading corrected for temperature, June 29% and 302, . = 383:0 
Reet eas chee bae Soh e aCe men nineutes ar Sewage Mere Teen July 34and 44, . = 957-0 
Difference of readings before and after adjustment, . . . . . . = 5740 
Mean balance reading corrected for temperature, June 19—134,. . . = 3965 
SSE caidas ex ease secant a roee oot canna een ae wien Soslas ae > June 154—274,. . . = 3960 
Mean change of reading for 14 days,. . . . : =— 05 
Mean reading, therefore, before adjustment, amesbapdih to J ai: La Pee 3 i2)51'3, 
Mic. Div. 
Mean balance reading corrected for temperature July 64— 184, = 966-4 
ere Apucnracctossnoscods os abbcosebses apes aosospasceen ULM PUSS. Gata a CRM ena ato) 
Mean change of reading forl4 days, .........:..=—89 
Mean reading, therefore, after adjustment, corresponding to July 134, . . . = 973-1 
The readings after adjustment are therefore greater than before adjustment, by 5775 
A comparison of the mean for the fortnight before adjustment, with that for the 
fortnight after adjustment, rejecting days of disturbance, and allowing for secular 
change, gave 577. 
Mic. Div. 
} 576-0. 
The readings after adjustment, are therefore considered greater than those 
bofore’adjustment; byer conse ceasnch deed. ciate cence tend lle Teend 
