355 



moments, varying the interval two, three, or four seconds, each way, 

 and sometimes throwing them into the half-second beats, and at others 

 into the whole-second beats at that place, as tests upon the series. 

 The reductions from Chicago mean solar to sidereal time, with the 

 difference of the rates of the two chronometers incorporated into the 

 calculations, give the fractions of a second which appear in the stated 

 differences of longitude between the two stations — the signals corres- 

 ponding to coincident beats of the two chronometers being the only 

 ones used in the computations. 



I will now proceed to state, in a brief form, the observations and 

 the results derived from them. 



The Observations for Time at Chicago. 



\st. 1858, June 20th. At Chicago Observing Station No. 2, in 

 latitude 41° 53' 50 ".5 N.: longitude 5h. 50m. 315.15 W. 



Sidereal chronometer No. 2557, fast: 



By 11 observations on u Lyrse, east (at I5h. 40m. m. s. 



sidereal) ..... 59 18.93 



By 12 observations on cc Bootis, west (at I6h. 13m. 



sidereal) ..... 59 18.32 



Result — Chronometer No. 2557, fast of sidereal time 



for this station (at 15h. 56m. sidereal) - -f 59 18.62 



By comparison — Chronometer No. 141, slow of mean 



solar time for this station (at 10/t. 00m. mean time) — 4 59.07 



2d. June 22d. Same Station, 



Sidereal chronometer No. 2557, fast; m. s. 



By 14 observations on u Lyrse, E. (at 15^. 36m.) 59 30.90 



By 16 observations on a Bootis, W. (at 16A. 10m.) 59 30.53 



Result — Chronometer No. 2557, fast of sidereal time 



for this station (at loh. 53m.) - . .{- 59 30.7I 



By comparison — Chronometer No. 141, slow of mean 



solar time for this station (at 9A. 48m. mean time) — 4 58.33 



