« НазадПродовжити »
We regret that we had not time to make a connection, by survey, from our astronomical station at Dunleith, to the stone monument on the east bank of the Mississippi river, erected to mark the western terminus of this boundary line. From a close reconnoissance, however, we infer that the latitude of this monument is about 42° 30' 20", and hence, that the monument is placed about one-third of a mile too far to the north.
XII. DUBUQUE, IOWA. This city is situated on the west bank of the Mississippi river, opposite to Dunleith, Illinois.
From a reconnoissance and bearings observed from several points in Dunleith, based on the latitude and longitude of our Dunleith station, as already given, we are enabled to give the approximate position of Dubuque as follows. The distance between the two points being, in a direct line, not more than one and one-fourth mile, viz.
CENTRE OF THE CITY OF DUBUQUE. Latitude,
42° 29' 55" N. Longitude, west of the meridian of Greenwich, 6h. 02m. 40s. Equal, in arc, to
90° 40'00" .
XIII. FULTON, ILLINOIS. This city is situated on the east shore of the Mississippi river, 136 miles west of Chicago, by the track of the Chicago, Dixon, and Iowa Air Line Rail Road, of which it is, at present, the western terminus. Immediately opposite is the city of Lyons, situated on the west shore of the Mississippi. Observations were made at both places, and the observing stations were connected by a triangulation and azimuths, derived from an observation on Polaris (a Ursæ Minoris). From the astronornidal station at Fulton, to that at Lyons, is 3595.5 feet, on an azimuthal course of N. 68° 43' W. Hence the Lyons station is
+ 12".89 north of the parallel and + 44".29 in arc, = + 28.95 in time, west of the meridian of the Fulton Station. We shall have oc. casion to use this difference of latitude in applying a common correction (-1".92 in the one case, and +1".92 in the other), to the observed latitudes of these two stations, in order to render the difference of their latitudes consistent with the result of the survey. The survey gave us, also, the longitude of the Lyon's Station, based on that of the
Fulton Station, derived from comparison by means of the two chronometers, with the longitude of Chicago.
We now proceed to give the observations at Fulton :
Position of the Fulton Station. From this station to the intersection of the middle of Base Street, with the middle of Cherry Street, is N. 53° 24' 53" W. (true) and the distance is 302 feet. Hence the reduction in latitude is + 1".71, and in longitude + 3".20 in arc, or + 08.214 in time.
1st. Observations for the Latitude. 1858, March 24th. By 19 circum-meridian altitudes of Polaris (lower
transit) north, combined with 26 circum-meridian altitudes of a Virginis, south,
41 52 03.25 Correction due to survey, connecting with the Lyons observing station,
Latitude of station adopted,
41 52 01.33 N.
2d. Observations for the Time. 1st. 1858, March 24th. Mean solar chronometer was fast of mean solar time at apparent noon: By 2 pairs of equal altitudes of the sun's lower limb, + 5m. 10.72s.
By comparison-Chronometer No. 2557, was fast of
sidereal time for this station at apparent noon (say at 0h. 14m. sidereal time)
+1 00 13.75
2d. 1858, March 28th. Sidereal chronometer No. 2557, fast : By 10 observations on a Tauri, west, and 9 observa
tions on B Tauri, also west (at 8h. 40m.) +1 00 31.93 By 24 observations on e Bootis, east (at 10h. 30m.) + 1 00 31.87
Result-Chronometer No. 2557, fast of sidereal time
for this station (at 9h. 35m. sidereal time)
+1 00 31.90
By comparison-Chronometer No. 141, was fast of
mean solar time for this station (at 9h. 10m.
+ 5 07.94
3d. The Longitude. 1. By the transmission of mean solar chronometer No. 141, from Chicago to Fulton and back to Chicago, between the 22d and 29th of March, 1858. Rate, during the elapsed time, — 08.744 per mean solar day. 1858, March 24th.-Chronometer No. 141, was fast of Fulton mean solar time at apparent noon,
+ 5 10.72 1858, March 22d.-Slow of Chicago
mean solar time at Chicago, apparent noon,
- 4 56.26 Elapsed time, 2.007 mean solar days,
allowing for diff. of longitude of stations, X 08.744,
Chronometer No. 141, slow of Chi.
cago mean time, at the period of Fulton apparent noon, of March 24th, 1858,
(a) Difference-Fulton, west of Chicago,
+ 10 08.47
2. By sidereal chronometer No. 2557: 1858, March 24th.-Chronometer fast of Fulton si. dereal time (at Oh. 14m. sidereal time)
+1 00 13.75 1851, March 22d.-Fast of Chicago
sidereal time (at Oh. 06m. 44s. sidereal time)
+049 55.67 Elapsed time, allowing for diff. in long.
= 2.012 sider. days, x + 4s.23, the rate per sidereal day,
= + 8.51
Chronometer No. 2557, fast of Chi.
cago sidereal time, at the period of the Fulton time observations,
+ 50 04.18
+ 50 04.18
(6) Difference.-Fulton west of Chicago,
+ 10 09.57
If we take the time-observations at Fulton, of the 28th March, 1858,
as the basis of the comparisons, a similar process to the above, will give us the following additional results, viz.(c) By mean solar chronometer No. 141 : Fulton west of Chicago,
+ 10 08.96 (d) By sidereal chronometer No. 2557: Fulton west of Chicago,
+ 10 09.15
Mean of the 4 results, a, b, c, d,
+- 10 09 04 + 5 50 30.99
1st Determination. Longitude of Fulton observing station, by the run of
the two chronometers, west of the meridian of Greenwich,
6 00 40.03
On this journey, the chronometers were transported in the rail cars. Each chronometer was carried in a small basket, resting within a nest of elastic curled hair, with a lining of soft green baize between the hair and the chronometer. Every pains was taken to protect them from jolts and all kinds of rough usage. From long experience, I believe that good results for differences of longitude, derived from transporting chronometers, depend much more upon this sort of care and attention to them, than upon any other circumstances attending the operation. A few seconds of time are easily lost by careless handling of the chronometers.
In the present month of June, 1859, 1 determined to test the above result for the longitude, by the method more recently followed, of transmitting time-signals by the electric telegraph.
For this purpose, the time-observations of Chicago, given under the dates of June the 22d and 24th, and those now to be given under the date of June 23d, together with the signals, were made. 1859, June 23d. At the Fulton Observing Station, already
described. Sidereal chronometer No. 2557, fast:
1st Set. Before the Signals. By 8 observations on a Lyræ, east (at 15h. 20m.)
1 51 04.00 By 12 observations on a
(12) Canum Venaticorum, west (at 16h. 00m.) 1 51 04.21
1st Result-Chronometer No. 2557, h. m. fast (at 15h. 40m.)
1 51 04.10
+ 1 51 04.10 2d Set. After the Signals. By 14 observations on & Bootis, west (at 18h. 03m.)
1 51 04.47 By 10 observations on 3 Cygni, east (at 18h. 23m.)
1 51 04.49
2d Result-Chronometer No. 2557,
fast (at 18h. 13m.)
1 51 04.48
+1 51 04.48
Result adopted-Chronometer No. 2557, fast of si.
dereal time for this station (at 16h. 56m.)
+1 51 04.29
The above result, and the results of the time-observations at Chicago of the 22d and 24th of June, applied to the telegraphic signals, give us a second determination of the longitude of our Fulton Station, as follows, viz.
Determination of the Difference of Longitude between Chicago and
Fulton, Illinois, by electric signals for comparisons of time, June 23d, 1859. Sidereal Chronometer No. 2557, fast, of Fulton, sidereal time, (at 16h. 29m. 23s. sidereal time), 1h. 51m. 04s.16. Rate
per sidereal day, + 73.025; or per sidereal hour, + 08.2927. Mean solar Chronometer No. 141, slow, of Chicago, mean solar time (at 10h. 32m. 20s. mean time) 4m. 50s.03.
Rate per mean solar day, Os.19; or per mean solar hour, 08.0079.
1st.-Chicago signals recorded at both stations.
Times of signals
Chicago by mean solar Chronometer
Correct Chicago mean solar
time of Chicago signals.
Chicago signals, as noted
at Fulton by sidereal Chronometer
Difference of Longitude by each signal.Fulton west of the meridian of Chicago obsery. ing station No.3.
h. m. 8.
8. 10 27 30 10 32 20.03 18 20 27 16 29 22.84 16 39 31.57 0 10 08.73 10 30 30 10 35 20.03 18 23 27.5 16 32 23.33 16 42 32.06 0 10 08.73 10 33 30 10 38 20.03 18 26 28 16 35 23.82 16 45 32.55 0 10 08.73 10 45 30 10 50 20.03 18 38 30 16 47 25.75 16 57 34.52 0 10 08.77 1st Mean.--Electric signals sent from Chicago to Fulton, 0 10 08.74