66 



Obseevation of Absolute Hokizontal Intensity, March 26. 1842. 



Observations of Deflection. 



Deflecting Bar 



Distance. 



Ft. 



5-25 W. 

 8-50 W. 

 8-50 E. 

 5.25 E. 



N. 

 End. 



w. 



E. 



E. 



W. 



E. 



W. 



W. 



E. 



Mean 

 Readings 



of 



Suspended 



Magnet. 



Sc. Div. 



36-61 

 461-34 

 308-13 

 186-98 

 307-09 

 187-35 



35-45 

 458-68 



BiFiLAR Mag- 

 netometer. 



Mean 

 Deflection, 



Sc. Div. 

 212-37 



60-57 



59-87 



211-61 



Read- 



ThermO' 

 meter. 



Sc. Div. 

 153-9 

 150-3 

 156-2 

 149-2 

 151-2 

 152-3 

 151-3 

 153-1 



54-0 

 54-4 

 55-2 

 54-8 

 55-8 

 560 

 56-2 

 56-3 



Observations of Vibration. 





60 



S. End 



Vibra- 



Moving W. 



tions. 



h. m. s. 



m. s. 



3 16 330 





21 35-4 





26 37-3 





31 39-4 



15 6-4 



36 41-6 



15 6-2 



41 43-6 



15 6-3 



46 45-9 



15 6-5 



S. End 

 Moving E. 



m. 

 16 

 21 

 26 

 31 

 36 

 41 

 47 



49-0 

 510 

 53-0 

 55-3 

 57-4 

 59-4 

 1-6 



60 

 Vibra- 

 tions. 



Bifilar Magnetometer 



6-3 

 6-4 

 6-4 

 6-3 



Time of 

 Obser- 

 vation. 



Read- 

 ings. 



18 30 

 21 

 23 30 

 26 

 28 30 

 31 

 33 30 

 36 

 38 30 

 41 

 43 30 

 46 



Sc. Div. 

 161-5 



166-6 

 166-8 

 166-0 

 164-5 

 162-3 

 162-2 

 159-5 

 1600 

 160-4 

 158-7 

 156-4 



Ther- 

 mome- 

 ter. 



56-0 

 560 

 56-0 

 56-0 

 55-9 

 55-9 

 55-8 

 55-7 

 55-7 

 55-6 

 55-5 

 55-4 



r = 5-25 feet. Mean deflection 21 1-99 Sc. Div. m = 2° 22' 14"-7 



7^=8-50 60-22 m' = 0° 40' 24"-4 



Observed mean time of one vibration, 1^= 15'-1058. 



Mean Bifilar, {xhermmn } ^^^'^^S deflections, | ^^Jo^gt } Heading corrected, 523-8*''- 

 Mean Bifilar, {^hCTmOTn } <i""°g vibrations, | ^550.3" } Reading corrected, 534-8*"- 



A "Y^ A 



Difference of Bifilar readings during deflections and vibrations corrected = 1 = 11-0 Sc. div. 



X w* 

 = -00137 in parts of force. 



TT TT 



==- = 0000994. (See Introduction for value of — , March 3. 1842.) 



c ' (at commencement) n -u ■• 

 Semi arc < , , ... > 01 vibrations. 



I at termination f 



Jos = 10° 

 \ct'= 6° 



^Length, a = 1-25 feet, 

 Deflecting bar, -^JBrcadth, b =00719 feet, 



(Weight, W = 6216-7 grains. 



From the formulae below there has been obtained X = 2-9662. 

 Moment of inertia K = ^1+^ W. 



t(i -f-5 -±^') =T, 

 V 9 r 16 / 



12 



time of vibration corrected. 



li^ (1 + ^ + ^^ =m X at the period of deflections. 



0-1) 



r'^ tan u' — r^ tan u m 

 2 {'/'^-r'^) ~ X' 



The hours of the deflection observations have not been registered. 



The arcs of vibration were not registered. The above have been estimated from a remembrance that Mr. 

 Russell used rather large arcs of vibration, and from other considerations. The times of vibration were obtained 

 from the clock in the observatory ; the rate is not registered, but it was generally very small. 



The notation and formulae above are those used in the Report of the Royal Society. 



