THE TRANSATLANTIC LONGITUDE. 



47 



VI. 



OBSERVATIONS AT CALAIS. 



The Hardy clock was used at this station, and the transit-instrument No. 8, which 

 had been employed with the same reticule at Mobile in 1858, and Eufaula in 1860. 

 The cumbrous structure of the clock gave much trouble to the observers, which was 

 increased by a couple of accidents. Some of the teeth of the escapement were bent, 

 in the transportation or otherwise, and the performance was unsatisfactory. Still 

 the most serious difficulties were obviated by the care and zeal of aU the members 

 of the party ; and although the time-determinations could not always be all that 

 they desired, and especially those on December 12 seem affected by some un- 

 explained source -of error, there is small doubt that had the operations continued for 

 another week these sources of discordance would have been removed. The deter- 

 minations on different dates are much more accordant than might have been 

 expected under the circumstances, and the probable error of the final result is small. 



The thread-intervals are derived from twenty-two complete transits, and the 

 values deduced from these observations have been combined with those found for 

 the same instrument and reticule from transits at Mobile in 1858, and Eufaula in 

 1860. These are given in the following table, in which the intervals previously 

 found are reduced to the scale corresponding to the Calais focus. 



Equatorial Thread-intervals of Transit No. 8. 





Mobile, 1858. 



Eufaula, 1860. 



Calais, 1866. 



Adopted. 



B, 



+ 37^925 



-|-37=.926 



-1-37^976 



-f37' 942 



b] 



35 194 



35 205 



35.214 



35.204 



B, 



32.664 



32.665 



32.611 



32,647 



B, 



29 9.59 



29.933 



29 986 



29.069 



b: 



27,214 



27, 215 



27 183 



27.204 



Ci 



21.728 



21 742 



21.810 



21.760 



c. 



19 069 



19 056 



19.047 



19.057 



■ C3 



16.286 



16 284 



16.271 



16 280 



c. 



13 644 



13 619 



13 583 



13.615 



< 



10 950 



10 930 



10 948 



10.943 



I>1 



5.546 



5 562 



5 528 



5.545 



D. 



-F 2.737 



+ 2.747 



-f- 2.706 



+ 2.130 



I>, 



—0.065 



—0 060 



—0.060 



—0.062 



D^ 



2.794 



2.796 



2.641 



2.740 



D. 



5 527 



5.532 



5555 



5.538 



El 



10 922 



10.909 



10.936 



10,922 



E3 



13.600 



13 594 



13.663 



13.619 



E3 



16 371 



16,378 



16.376 



16.375 



E4 



19.032 



19.035 



19,013 



19 027 



E. 



21 700 



21.686 



21.679 



21.688, 



El 



27.137 



27 113 



27.115 



27.122 



E 



29,871 



29.870 



29.850 



29.864 



E3 



32.591 



32.612 



32.626 



32 610 



E4 



35 305 



35 315 



35.321 



35.314 



e: 



—37.999 



—38.014 



—38.038 



—38,017 



