OF THE OBSERVATORY OF CAMBRIDGE BY GALVANIC SIGNALS. 



505 



Mean Time. 



A. m. m. t. 



May 16. 12.52 X fast 1.55,53 



21.28 — 



17. 



21.28. 

 2.12. 

 7.34. 



12.56. 



1.55,89 

 1.55,94 

 1.56,12 

 1.56,42 

 1.56,49 

 1.58,61 



May 16. 



17. 



12.46 U slow 3.35,04 



21.21 3.37,92 



2.16 3.39,60 



7.39 3.41,58 



9.45 3.42,37 



Mean Time. 



A. m. m. t. 



May 17. 13.22 X fast 1.58,61 



18. 



13.28. 



9-37. 



9-40. 

 13. 3. 

 13. 3. 



1.58,72 

 1.59,32 

 1.59,38 

 2. 1,15 

 2. 1,14 



May 17. 

 18. 



13.10 U slow 3.43,83 



9-43 3.54,76 



13.10 3.56,42 



13.10 3.56,40 



These results shew that on both days from 10 h to 13 h , that is, during the intervals 

 occupied in transporting the chronometers and taking the observations, W and U maintained 

 rates not materially differing from their general rates inferred from the comparisons on 

 May 16, 17, and 18, but that this was not the case with the Chronometer X. This 

 chronometer was selected for recording the signal-times because its rate was known to be 

 much smaller and generally more steady than the rates of the other two. The appearance of 

 its errors leads to the suspicion that half-seconds were gained during the transports by 

 tripping, and that the rates were in other respects good. I made a calculation of the 

 longitude on this supposition, assuming four half-seconds to have been gained in this way 

 on May 17 and three half-seconds on May 18, and I found that the longitude resulting from 

 the observations of May 17 would thus be diminished by S ,020, and that resulting from the 

 observations of May 18 be increased by S ,020, equal weights being given to the three chro- 

 nometers. As therefore the final result would not be affected, and as the above supposition 

 may be somewhat precarious, I have preferred trusting exclusively to the Chronometers W 

 and U. The calculations will therefore be made on the supposition that these chronometers 

 maintained uniform rates from the times of comparison with Hardy before leaving the 

 Observatory, to the times of comparison on returning to the Observatory, and errors of X 

 will be deduced by means of the comparisons made at the station, first from W's errors, and 

 then from U's errors. On May 17 from 9 h . 49 m to 12 h . 57 m , W gained S ,62, and on May 18 

 from 9 h . 48 m to 13 h . 3 m , the gain was S ,76. On the first day U lost l s ,46 from 9 h . 45 m to 

 13 h . 10 m , and on the second day the loss was l s ,66 from 9 h . 43™ to 13 h . 10 m . From these 

 data and the comparisons of X and U with W at the station the following errors of X may 

 be obtained. 



Mean Time. 



A. m. m. s. m. t. 



May 17. 10.30.. .X fast by W... 1.56,50... X fast by U... 1.56,53 

 10.45... ...1.56.52... ...1.56,55 



10.51... 

 12. 6... 



...1.56.53... 

 ...1.56,50... 



...1.56,58 

 ...1.56,47 



65—2 



