38 



Mr. Harvey on the Effects of Magnetism 



the former, and when the balance was at its mean distance from the 

 globe, the rates were very nearly equal. 



The preceding results are entered for the sake of a convenient 

 reference, in the following Table, together with the positions of 

 the time-keeper, with respect to the geometrical centre of the 

 attracting mass : 



The second chronometer B, was placed to the south of the ball, 

 with the centre of its balance in the magnetic meridian of the fer- 

 ruginous mass, and XII directed to the north, as represented in B, 

 Fio-. 1. This application of the time-keeper produced no altera- 

 tion of rate ; but on turning it a quadrant, so as to make the mag- 

 netic meridian of the ball form nearly a tangent to the rim of the 

 balance, as in B, Fig. 2, the rate was changed from — 7".6 to 

 — 6".9; the time-keeper having gained 0''.7 by the change. In 

 the next position, denoted by B, Fig. 3, the balance being again 

 in the magnetic meridian of the ball, and at its least distance from 

 it, the daily decrement was augmented to — 7".2, being only 0".4 

 less than the rate, when the balance Avas before placed in the 

 meridian, and at its greatest distance from the ball. No obser- 

 vations were made with the machine, by turning it through a 

 fourth quadrant. It appears, therefore, thatf the time-keeper B 

 underwent no alteration of rate, by ■placing the centre of its balance 

 in the magnetic meridian, and at its greatest distance from the attract- 

 ing body ; and only a mimite increment, tvhen at its least distance ; 

 nor ivas the change in the rate of the chronometer much greater 

 when a line draion from the middle of the balance was at right 

 angles to the meridian of the ball. This chronometer, therefore, from 

 its having probably a balance nearly free from the magnetic influence, 

 underwent but little alteration of rate, by its application to the iron 

 mass. The preceding results are arranged in the next Table : 



