379 



h. m. s. 

 Brought forward, + 01 06.30 



Reduction to the said steeple, ... -|- 0.03 



Steeple, west of the meridian of Chicago observing 



station No. 3, - - - - + 01 06.33 



Longitude of Chicago station No. 3, - - + 5 50 31.20 



Determination 3d. 



Longitude of the said steeple, west of the meridian of 



Greenwich, - - - - - 5 51 37.53 



Here are three singular coincidences in the determination of the 

 difference of longitude between two places derived from time observa- 

 tions made with a sextant and an arlificial horizon. We will present 

 a fourth and then a summary of the whole. 



I will first remark, that the time was obtained at Chicago afresh 

 on my return hither on the nightof thesame day (July 3d); that the equal 

 altitudes of the sun were observed and the signals passed, as will be 

 seen by reference to the preceding record of the Chicago observations. 



Late in the afternoon of July 5th, I was again summoned to go to 

 Milwaukee on business connected with the harbour improvement there. 

 I determined to make the journey the occasion of a fourth trial of the 

 difference of longitude, by a set of observations that should render it 

 entirely independent of the other three. Accordingly on the nightof 

 the 5th, I made the observations at Chicago given under that date in 

 the preceding record. 



My business in regard to the harbour improvement occupied me at 

 Milwaukee all day of the 6th, and until the time for the afternoon 

 train of cars to start for Chicago on the 7th. By that train I reached 

 Chicago in time to make the observations already given under that 

 date. They, and those of the 5th, gave a short run for the rale of the 

 mean solar chronometer No. 141, at Chicago, and they also gave the 

 absolute time for the meridian of Chicago within 2r| hours of the 

 mean period of the telegraphic signals of the 6th. 



After the duties of the day for the 6th were over at Milwaukee, I 

 made the following observations for the time at station No. 3. 



Two sets of time observations were made at that station this night, 

 one set before exchanging the telegraphic signals with Chicago, and 

 another set after those signals. 



