506 PROFESSOR CHALLIS, ON THE DETERMINATION OF THE LONGITUDE 



Mean Time. 



ft. m. m. t. m. ». 



May 18. 10.44.. .X fast by W...2. 0,03.. .X fast by U...2. 0,10 



10.47... ...2. 0,04... ...2. 0,10 



12. 5... I ...2. 0,05... ...2. 0,11 



Some of the comparisons were made under disturbance by railway noises. Giving double 

 weight to the results by Chronometer W, as depending on direct comparison with X, we 

 obtain as follows : — 



Method (A). 



ft. m. t. 



May 17. 11 mean time, X fast 1.56,52 



12 1.56,49 



May 18. 11 2. 0,06 



12 2. 0,07 



By these errors of X the signal-times were converted into Cambridge sidereal times, each 

 of which, compared with the corresponding Greenwich sidereal time, gives a separate deter- 

 mination of the longitude. Subjoined are the individual results classed in groups, according 

 as the signals were made at Greenwich or Cambridge. The reference numbers correspond to 

 the series-numbers in the lists of signal-times. In this calculation Mr Breen's observations 

 are not made use of. 



Determinations of the Longitude by the Signals of May 17. 



First Set. 



First Set— continued. 



