on the Rates of Chronometers. 



43 



On moving it through another quadrant, thereby presenting XII to 

 the North, the daily aberration became — 6".0, having gained 

 I".2 by the last movement. Lastly, by detaching the time-keeper 

 from the iron mass, the rate became — 6".6. This chronometer, 

 therefore, both gained and lost in its different positions with respect 

 to the iron 7nass; — losing by its change of position from Fig. 7 to 

 Fig. 8 ; preserving nearly a stationary rate from the last-mentioned 

 position, to Fig. 9 ; and gaining by its removal from Fig. 9 to Fig. 

 10. The first application also of the chronometer to the attracting 

 mass, occasioned it to gain, and its removal from it, to lose. 



The third chronometer C, which formerly occupied a position 

 to the East of the ball, over the magnetic parallel of 45° N., was 

 now placed to the West of it, with the centre of its face in a hori- 

 zontal plane passing through the centre of the globe, and also in a 

 vertical plane passing through the same point, and at right angles 

 to the magnetic meridian. The detached rate was — 8".4, and 

 which only underwent a minute change to — 8".2, by placino- the 

 machine as in C, Fig. 7, with its balance nearest the ball ; but, on 

 turning the chronometer a quadrant, in order that it might 

 occupy the situation C, Fig. 8, the rate declined a second, amount- 

 ing to — 9".2 ; and a still more considerable declension was pro- 

 duced, by causing the centre of the balance to be placed in the 

 magnetic meridian of the attracting mass, and at the same time at 

 its greatest distance from it, as in Fig. 9, the rate amounting in 

 this position to — 1 1",4 ; but on turning the time-keeper through 

 another quadrant, in order for it to occupy the position of C, 

 Fig. 10, a very great acceleration took place, the rale amounting 

 to — 6".5. By finally detaching the chronometer from the attrac- 

 tive influence, the rate returned to — H".l, being a greater losing 

 rate than originally displayed by the machine, before its applica- 



