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1st.-Chicago signals recorded at both stations.

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2d.—Dunleith signals recorded at both stations.

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h. m. S. Th. m. S. h. m. 8. h. m. 8. Th. m. 8. h. m. 8. 11 47 23.5 12 06 00 (12 10 42.93|10 21 07.3910 09 0.971 012 04.42 11 50 24 12 09 00 (12 13 42.93 10 24 07.88 10 12 03.45 0 12 04.43 11 53 24.5 12 12 00 12 16 42.93 10 27 08.37 10 15 03.94 0 12 04.43 11 56 25 12 15 00 12 19 42.93 10 30 08.87|10 18 04.43 0 12 04.44 2d Mean.-Electric signals sent from Dunleith to Chicago, - 0 12 04.43 1st Mean.-Electric signals sent from Chicago to Dunleith, as above, - -

- - 0 12 04.41 Result: Dunleith station No. 2, is west in longitude of Chicago

station No. 3, by a mean of the two sets of signals, + 0 12 04.42 Longitude of Chicago Station No. 3,

+ 5 50 31.20

Determination 2d.
Longitude of Dunleith observing station, west of the

meridian of Greenwich, by this ad determination
of Feb. 22d, 1859, - - - - 6 02 35.62

Determination 1st.
By the observations and signals of February 21st, as
above given,

· · 6 02 35.88 Result adopted—Longitude of the Dunleith observing

station, west of the meridian of Greenwich, by a
mean of the two determinations,

• 6 02 35.75 Equal, in arc, to

90° 38' 56''.25 Latitude of this station, as before given, . 42° 29' 44".9 N.

Result_By the measured offset and azimuth, from this station, given at the beginning of this article XI. the most northern cupola on the top of the ticket-office of the rail road depot, is inLatitude . .

42° 29' 42".5 N. Longitude, west of Greenwich,

6h. 02m. 35.8s. Equal, in arc, to

90° 38' 57" W.

Dupleith is at the north-western terminus of the Illinois Central Rail Road, on the east bank of the Mississippi river, and occupies the site of the old Indian village of Sinipi. Extensive earth works, consisting of mounds thrown up in oval forms by the tribe which formerly resided here, still exist at Dunleith, in a state of persect preservation. We had no time to devote to them that minute exploration which would no doubt show their contents to be similar to those of the numerous Indian mounds examined by Professor J. A. Lapham, of Milwaukee, and described in his valuable memoir, published in the year 1855, by the Smithsonian Institution, under the title of “THE ANTIQUITIES OF WISCONSIN.”

The position of Sinipi (now Dupleith), is laid down on the map of Nicollet, in latitude 42° 36' north, and in longitude, west of the meridian of Greenwich, 6h. 02m. 38.6s. = 90° 39' 39''. Nicollet did not, however, make any astronomical observations at this or any other point on the Mississippi, between the Head of the Upper Rapids, below Port Biron and Parkhurst,” and “ Prairie du Chien. We inser from his report, that the extensive reach of the Mississippi, from latitude 41° 36' 08" to latitude 43° 03'06'', was laid down on his map, from the surveys made under the direction of the General Land Office of the United States, checked by his observations made at the two extreme points above mentioned. (See his table of Geographical positions, page 123 of Senate Doc. No. 237, of the 26th Congress, 2d Session.) Nicollet's longitude, thus derived, agrees very closely with ours; but in latitude he is 6' 18" = 74 miles north of us. Dubuque is placed equally out of position, in latitude, on his map; but it appears to be very correct in longitude.

In the last map issued from the War Department of the “ Territory of the United States, from the Mississippi to the Pacific Ocean,” these cities are laid down correctly in longitude, but they are placed four minutes, = 4% miles too far north in latitude.

The boundary line between the State of Illinois on the north, and the State of Wisconsin on the south, is defined to be along the parallel of 42° 30' of latitude.

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

VOL. VII.-I

2d.-Prairie du Chien signals recorded at both stations.

Times of Times of signals given Prairie du Chien at Prairie du signals, as noted Chien by at Chicago

sidereal by mear solar Chronometer Chronometer

No. 2557. No. 141.

Chicago correct mean solar time of Prairie du Chien signals.

Difference of

Longitude by Chicago Prairie du Chien each signal. reduced

correct Prairie du Chien sidereal time sidereal time west of the me of

of Prairie ridian of ChiPrairiedu Chien du Chien cago observing signals.

signals. station No. 2.

h. m. 8. h. m. 8. h. m. $. h. m. 8. h. m. 8. h. m. 8. 20 41 30 12 07 53 12 12 37.51 19 39 53.68 19 25 50.26 0 14 03.42 20 44 30.5 12 10 53 12 15 37.51 19 42 54.17 19 28 50.75 0 14 03.42 20 47 31 12 13 53 12 18 37.51 19 45 54.66 19 31 51.24 0 14 03.42 20 50 30.5 12 16 53 12 21 36.51 19 48 54.16 19 34 50.73 0 14 03.43 2d Mean.—Electric signals sent from Prairie du Chien to Chicago, 0 14 03.422 1st Mean.-Electric signals sent from Chicago to Prairie du Chien,

as above, - - - - - - - - - - 0 14 03.436

Result:-Prairie du Chien observing station is west, in longitude,

of Chicago observing station No. 2, by a mean of the two sets

of signals, - - - - - - - - +0 14 03.429 Longitude of Chicago observing station No. 2, west h. m. S. of the meridian of Greenwich,

+ 5 50 31.15

Longitude of Praire du Chien observing station, west of the meridian of Greenwich,

• 6 04 34.58 Equal, in arc, to . .

91° 08' 38".7 W. Latitude of this station, as above,

43° 02' 01".35 N.

The above determination will be found, we think, to correspond very nearly with that of Mr. J. N. Nicollet, derived by him from obser. vations made in the year 1839, while employed in exploring the hy. drographical basin of the Mississippi. His station was the American Fur Company's house, near Fort Crawford. An interesting discus. sion of the several observations which led him to the longitude which he adopted for that station, will be found in his report at page 117, of Senate Document No. 273, of the 26th Congress, 2d Session, printed in the year 1843.

He there states the longitude of that point to be, h. m. s. West of the meridian of Greenwich,

604 35.55 Equal, in arc, to

91° 08' 53".25* In his table of geographical positions, however, at page 123, he states that position to be in Latitude · · ·

43° 03'06" N. Longitude, west from Greenwich,

6h. 04m. 37.3s. * Erroneously printed in that document, 93°, &c.

I only spent the night in observing at Prairie du Chien, and was obliged to leave that place early the next morning, on my return to Chicago. Hence I had no opportunity for making any survey to connect our two stations, and thus determine accurately their relative positions. In looking up the Mississippi, however, from my station, I observed that its course upward appeared, when compared with the direction of the North Star (Polaris) to be a very little west of north. The difference of our longitudes, reduced to a common point, is not probably more than one second of time; and, judging by the eye, of the distance from my station to the Fur Company's old house, our latitudes appear to agree very closely.

XI. DUNLEITH, ILLINOIS. Station.—One hundred feet east from the left shore of the Mississippi river, between the freight depot and the passenger house of the Northwestern terminus of the Illinois Central Rail Road. From the ob. serving station to a point perpendicularly under the most northern of the two cupolas on the north end of the ticket office, of this rail road depot, is S. 13° W. 250 feet, horizontal measurement.

1st. The Latitude. 1859, February 22d. By 37 circum-meridian altitudes of B Orionis, south,

combined with 24 altitudes of Polaris (a Ursæ Minoris,) north, .

. . 42 29 45.16 Same night.-By 26 circum-meridian altitudes of a

Hydræ, south, combined with 14 other altitudes of Polaris, observed 5 hours later than the previous set, · ·

• 42 29 44.65

Result—Latitude of station,

42 29 44.9 N.

2d. Observations for the Time. 1859, February 21st. Sidereal chronometer No. 2557, fast :

1st Set. Before the telegraphic signals. By 10 observations on a Arietis, west h. m. $. (at 6h. 16m.)

- 1 38 14.48 By 11 observations on g' Leonis, east (at 6h. 39m.)

- 1 38 14.67

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