BappickER—On the Influence of Magnetism on the Rate of a Chronometer. 37 
back to the Observatory in September 1839, because its rate underwent changes in 
the proximity of an iron door. It was compared daily, and after each comparison 
turned by 90° in azimuth. Since each cycle of observations is only four or five 
days, Airy considers it hardly probable that the comparison of rates is sensibly 
affected by the gradual changes of rate peculiar to all chronometers. The ob- 
served values which show, as Airy remarks, that the chronometer is, generally 
speaking, a good one, are contained in the following Table :— 
Position oF Fieure XII. 
Date. 
North. : East. ~ South. West. 
1839, 
October 
FOoenDn NAOnF 
| 
cs 
_ 
| 
| 
| 
= 
November 1 -— 6°2 —- = 
No. of Days 8 7 7 7 
