Total Eclipse of August 7, 1869. 195 



The following quantities measured from the chrono- 

 graph sheets, will show the progress of the phenomena : 



Mattoon Mean Time, 

 h. m. s. obs. 



Lunar mountain in contact with the sun 4 11 07.5 H. 



Beginning of the eclipse 4 11 16.8 H. 



« , 4 11 15.2 S. 



Red flame seen 5 10 50.0 H. 



Bailey's Beads 5 11 23.6 H. 



« 5 11 22.4 S. 



Beginning of totality * 5 11 28.5 H. 



« * 5 11 28.0 S. 



End " " 5 14 11.3 H. 



Duration " " 2 42.8 H. 



" " « (Naked eye) 2 40.0 



Disappearance of red flame 5 20 06.5 H. 



Red flame seen after totality 5 55.2 H 



End of eclipse 6 09 09.4 H. 



Duration of Bailey's Beads 04.9 H. 



« " " « 05.5 S. 



* Record on the chronograph sheet very faint. 



The initials H, and S, refer to the observation of Hough 

 and Swift. 



These observations depend on Dudley Observatory time, 

 using the longitude of Mattoon as determined by the U. S. 

 Coast Survey, viz : 58m. 33.0s. west of Dudley Observatory. 

 The probable error of the Dudley observatory clock, will 

 not exceed ± 0.20s. 



The Armature time for the "repeaters" and "relays" 

 was found to be 0.21s. This quantity has been used in 

 the comparison of the chronographs, at Dudley Observa- 

 tory and Mattoon. 



Great precision, in the observation of the beginning or 

 end of a solar eclipse, is not at present attainable by any 

 method. Until we have a complete chart or delineation 

 of the moon's edge, it will be impossible to observe the 

 contact of the sun's and moon's limb, within one second 

 of time. 



[Trans. vi.~\ 25 



