70 SIR WILLIAM THOMSON ON THE 
Diagram XVI. 
July 26, 4' 1 20 m to 5 h 10 m . 
Stretching weight, 14 lbs. 
Zero of magnetometer, at beginning 100, at end 100. 
Weight off and on, final reading rose from 750 to 830. 
Diagram XVII. 
July 26, 5 h 20 m to 6 h 10 m . 
Stretching weight, 14 lbs. 
Zero of magnetometer, at beginning 100, at end 100. 
Diagram XVIII. 
July 28, l h 25 m to 2 h 15 m . 
Stretching weight, 9 lbs. 
Zero of magnetometer, at beginning 100. 
Diagram XIX. 
July 28, 4 h 45 lu to 5 h 35 m . 
Stretching weight, 9 lbs. left on from end of No. IX. 
Zero of magnetometer, at end 105. 
Diagram XX. 
July 28, 5 h 20 m to 6 h 0 m . 
Stretching weight, 10 lbs. 
Zero of magnetometer, at beginning 105. 
Diagram XXI. 
July 30, 12 h 40 m to l h 20 ra . 
Stretching weight, 10 lbs. left on 42 hours from preceding No. XI. 
Zero of magnetometer, at end 105. 
Diagram XXII. 
July 30, 4 h 20 w to 5 h 10 m . 
Stretching weight, 16 lbs. 
Zero of magnetometer, at beginning 105, at end 105. 
Diagram XXIII. 
July 30, 5 h 20™ to 6 h 10 m . 
Stretching weight, 16 lbs. 
Zero of magnetometer, at beginning 105, at end 105. 
Note .—This experiment (XXIII.) was intended to be a continuation of the preceding. 
The magnetometer zero at the beginning was found, without taking off the weight, by 
drawing the wire aside ; but the disturbance thus occasioned when the wire was 
replaced raised the final reading of No. XXII. from 690 to 712, the initial reading of 
No. XXIII. 
The experiments represented in the six diagrams which follow were each repeated 
without stopping, and the repeat is represented by the dotted lines. 
