44 Mr. Harvey on the Effects of Magnetism 



tion to the iron mass. This chronometer, therefore, both gained 

 and lost, as was also determined in the first course of experiments. 



The fourth chronometer D, was placed to the east of the ball, 

 in a vertical plane passing through its centre, and with the plane 

 of the balance in the horizontal plane, supposed to pass through 

 the same point, as represented in D, Figs. 7 and 12. In the 

 former experiment this time-keeper was situated to the west of the 

 ball, in the same vertical plane, but elevated so as to be over the 

 magnetic parallel of 45° North. The first application of the chro- 

 nometer to the action of the ferruginous mass, communicated an 

 increment to its rate, from + 6".5 to + 7".3, the line joining the 

 centres of the time-keeper and balance, being in a plane parallel 

 to the magnetic meridian of the globe. By turning the chrono- 

 meter however, through a quadrant, so as to bring the before- 

 mentioned line into the vertical plane, passing through the centre 

 of the ball, and at right angles to the magnetic meridian, as in D, 

 Fig. 8, the daily variation underwent a decrement, it being +6".7; 

 and on turning the machine into the position denoted by D, Fig. 9, 

 where the line connecting the centres of the time-keeper and 

 balance was again parallel to the meridian of the ball, a farther 

 declension was found in the rate, it amounting to -{• 5".l ; but, on 

 brino-ing the time-keeper into the situation represented by D, 

 Fig. 10, the rate again recovered itself, it amounting to + 7".l ; 

 and, on removing the time-keeper from the effect of the attractive 

 influence, the rate again declined to -|- 5".7. Hence it appears, 

 that the action of the magnetic power on this chronometer, was to 

 occasion a)i increase of rate, in all its situations excepting one, 

 where a declension took place ; and that the entire suspension of the 

 attracting influence occasioned also the rate to diminish. 



