22 PROCEEDINGS OF THE AMERICAN ACADEMY 



The first contact was well observed, but the recorder did not notice 

 the signal, and the time is derived by estimate. According to the 

 observer, the signal was given half-way between the last two signals 

 of Professor Pickering, whose own estimate, however, placed it six 

 seconds later. The mean of these estimates was adopted. 



The third and fourth contacts were well seen and recorded. The 

 time given for the third contact is that when the diminishing thread of 

 light at the place of egress definitely broke. Eighteen seconds earlier 

 contact had certainly not yet occurred. 



Eight seconds previous to the time of fourth contact it was evident 

 that the egress had not been completed. 



J. R. Edmands. 



The telescope was one borrowed from Dr. E. T. Caswell, of Provi- 

 dence, R. I., and originally owned by Dr. Alexis Caswell, of Brown 

 University. It was attached to a portable equatorial mounting (with- 

 out clock) belonging to the Observatory. The observations at ingress 

 were made on the east balcony of the dome, and at egress on the west 

 balcony. The eyepiece was negative, and the light was reduced by 

 one shade-glass placed near the focus of this eyepiece at second con- 

 tact, and by three shade-glasses, one on each side of the focus and one 

 next the eye, at the third and fourth contacts. 



The chronometer used in recording these observations, as well as 

 for those of Mr. W. H, Pickering, was Frodsham 3451, regulated to 

 sidereal time. This is an excellent instrument, of much value in the 

 work of the Observatory Time Service. 



At first contact the rapid changes in the opacity of the clouds pre- 

 vented observation of the phenomenon, as the observer had no wedge 

 of shade-glass, and could not readily control the brightness of the 

 field. At second contact, the recorder found it impracticable to note 

 the times from the signals of the two observers, and the assumed times 

 are derived by estimate. The original estimate of the time of the 

 signal " Past " was derived from an inspection of the chronometer 

 made immediately after the observer learned that no record had been 

 secured. But he was satisfied, on consideration, that this first estimate 

 allowed too little for the interval between the signal and his inspection 

 of the chronometer ; besides which, his signal " Past " must have been 

 given an appreciable time after the contact itself. His last signal, 

 " Not yet," preceded the signal " Past " by about ten seconds. On 

 these accounts, he estimated the observed time of contact, which has 

 been entered in the Table, as five seconds earlier than the original 



