40 - Mr. HsLVvey on the Effects of Magnetism 



The fourth chronometer employed was D, in a similar situation to 

 thepreceding, on the western side of the ball, as D, Fig. 1, or D, Fig. 6. 

 The detached rate of the machine was + 5".0, and when it occu- 

 pied the position of D, Fig. 1, the mean of five days' observations, 

 gave a rate of +4". 9; the iron mass having scarcely produced 

 any effect. By turning the time-keeper, however, a quadrant, so as 

 to bring the centre of the balance into the magnetic meridian, and 

 the east and west plane touching its circumference as D, Fig. 2, 

 the rate augmented to +6".3 ; and, by again bringing the centre of 

 the balance into the last-mentioned plane, as represented in D, 

 Fig. 3, a farther acceleration took place, the rate being found to 

 be -l-7".8 ; but on turning it through another arc of ninety degrees, 

 corresponding to the situation D, Fig. 4, the daily alteration de- 

 clined to -t-7".0; and, on finally detaching the chronometer from 

 the ferruginous mass, its rate became +6". 5; having increased 

 its former detached rate-|-l".5, in consequence of the experiment. 

 Hence it appears that the application of this chronometer to the 

 attracting mass scarcely produced any effect in the position denoted 

 by Fie/. 1 ; but an acceleration of its rate took place in the situa- 

 tions represented by Figs. 2, 3, and 4 ; and by removing the time- 

 keeper from the magnetic influence, the rate declined, though not to 

 the same degree. 



The fifth chronometer E, was also placed on the western side of 

 the ball, as in E, Fig. 1 , having the middle of its face in a vertical 

 plane passing through the centre of the sphere at right angles to 

 the magnetic meridian, and also in a horizontal plane, passing 

 through the same point. In this situation of the time-keeper, the 

 line joining the centre of its balance and the centre of the chrono- 



