on the Rates of Chronometers. 



39 



The next chronometer C, was placed on the eastern side of the 

 iron sphere, with the middle of its face in a vertical plane passing 

 through the centre of the ball, and at right angles to the magnetic) 

 meridian ; and moreover, so elevated, that a line, joining the centre 

 of the face and ball, might intersect the magnetic parallel of 45° N, 

 as represented in C, Fig. 6. The detached rate of this time 

 keeper was — 7".2 ; but when the centre of the balance was 

 brought into the East and West plane, so as to be at its least 

 distance from the attracting mass, as denoted by C, Fig. 1, the 

 rate altered to — 6".8 ; and on turning the chronometer through a 

 complete semicircle, into the position of C, Fig. 2, thereby bring- 

 ing the middle of the balance again into the last-mentioned plane at 

 its greatest distance from the iron ball, the losing rate increased to 

 — 7"5. By again turning the time-keeper through a quadrant, in 

 order to bring the line joining the centres of the chronometer and 

 balance, into the magnetic meridian, as C, Fig. 3, the daily aber- 

 ration became — 6".5 ; and, on afterwards turning it through an 

 entire semicircle, into the position denoted by C, Fig. 4, the centre 

 of the balance being still in the magnetic meridian, the daily rate of 

 the time-keeper changed to — 8".8 ; and, by detaching it altogether 

 from the influence of the iron, the daily aberration was found to be 

 — 8".4. This chronometer, therefore, gained in the positions cor' 

 responding to figures 1 and 3, but lost in those represented by 2 

 and 4. 



Chronometer C in a Vertical Plane passing- through the Centre of the Iron 

 Shell, at right Angles to the Magnetic Meridian, and to the East of it. 



Distance of the 

 Vertical Axi:- of 

 tkisOhrouoniei«r, 

 from Centre ' 

 Shell. 



7 Inches. 



Elevation of IIm 

 Centre of llie 

 Face, above tlit 



8.5 Inches. 



■ 7".2 



Rate in 

 Fig. 1. 



-6".8 



Rate in 

 Fig. 2. 



-7".5 



Rate in 

 Fig. 3. 



-6".5 



Rate in 

 rig. 4. 



Dutiiched 

 Rate. 



- 8''.8 -8''. 1 



