No. 6.] INTRODUCTION. CHRONOMETERS. XL VII 



10. Increase of brightness very slow. l.n>4 later Sat. tolerably bright. 



11. Calculated time for D 2h 17 42". Observed continually till 2b 28m, but no de- 

 crease of brightness perceptible. Ceased for a while, but between 2b 42 m and 

 2h 45m S a t. as bright as before after which we left the Satellite to its fate. 



12. Calculated time for D Hw 20h 6m 5a. Observed til 20t> 10", unchanged, some- 

 what feebler than the other Satellites. Calculated time for R Hw 2H> 16m 29s ; 

 observed 21 11 ll m -20 m , but no increase of brightness. 



13. 26 9 later brightness estimated as 40 s before the moment noted for D. At 24 h 34 m 

 27 s the Sat. approached to the usual brightness. 



14. First glimpse. l m 33 s later same brightness as the Satellite to the left of Ju- 

 piter [Sat. IV]. 



15. Had just moved the telescope ; as soon as it had come to rest, the Sat. was seen. 



16. Observation begun at 14' 1 3m. 



17. Waited for R till 12'i 40m, but Sat. not visible; cirrostratus. 



Influence of Temperature. 



As there were in each of the three years of the expedition periods of 

 several months without any determination of the Greenwich Time, it was 

 necessary to examine the general rate of the chronometer and its dependence 

 on temperature. For this purpose the two other chronometers must also be 

 taken into consideration. From the journal of daily comparisons the following 

 Table d was formed, containing the difference Kt Hw and IvHw together 

 with the daily relative rate of each. The last column (t) gives the mean 

 temperature (Centigrade) of the interval. From the curves registered by the 

 thermograph in Mr. Scott-Hansen's cabin the mean temperature for every day 

 was taken out by inspection and reduced to the chronometer-shelf by means 

 of the daily comparisons with the lower thermometer. The temperatures in 

 Table d are means for 10 days (the intervals between the comparisons are 

 in some few cases 9 or 11 days). As the thermograph was taken down 1896 

 Aug. 10 the temperature for the last 11 days is more uncertain. 



