1st Result. Before the signals

Chronometer No. 2557, fast (ath. m. $.
6h. 27m.)

- 1 38 14.57 h. m. 8.

--- +1 38 14.57 2d Set. After the telegraphic signals. By 13 observations on a Bootis (Arctu

rus) east (at 10h. 37m.) - 1 38 15.60 By 14 observations on 3 Geminorum,

west (at 11h. 11m.) . . 1 38 14.88 2d Result. After the signals

Chronometer No. 2557, fast (at
10h. 54m.) . . . 1 38 15.24

--- +1 38 15.24

Result adopted-Chronometer No. 2557, fast of si

dereal time for this station (at 8h. 40m.) Feb.
21st, 1859 · · · ·

.+1 38 14.90

1859, Feb. 22d. At the same Station. Sidereal chronometer No. 2557, fast :

1st Set. Before the telegraphic signals. By 10 observations on a Arietis, west h. m.

(at 6h. 03m.) . . 1 38 19.55 By 10 observations on y' Leonis, east

(at 6h. 31 m.) - - 1 38 20.09 1st Result. Before the signals

Chronometer No. 2557, fast (at 6h. 17m.) . .

1 38 19.82 h. m. S.

-- +1 38 19.82 2d Set. After the telegraphic signals. By 14 observations on B Geminorum,

west (at 11h. 02m.) . . 38 20.52 By 11 observations on a Bootis, east (at 11h. 26m.)

- 1 38 20.79 2d Result. After the telegraphic sig.

nals--Chronometer No. 2557,
fast (at lih. 14m.) . . 1 38 20.65

+1 38 20.65

Result adopted-Chronometer No. 2557, fast of si.

dereal time for this station (at 8h. 46m.) Feb.
22d, 1859,

h. m. 8. +1 38 20.23

The first is derived from the time-observations made at that station, and the signals interchanged with Chicago, on the night of Feb. 21st. The second is derived from the similar observations and signals made on the night of Feb. 22d. They both depend in part upon the run of the mean solar chronometer No. 141, while at rest at Chicago as ascertained by the time-observations made there on the nights of Feb. 20th and 23d, already given.

The telegraphic signals, and the results, for the 1st determination, are as follows, viz.

Determination of the difference of Longitude between Chicago and

Dunleith, Illinois, by electric signals for comparisons of time, February 21st, 1859. Sidereal Chronometer No. 2557, fast, of Dunleith, sidereal time, (at 9h. 41 m. sidereal time,) ih. 38m. 14.90s.

Rate per sidereal day, + 58.308; or per sidereal hour, + 08.221.

Mean Solar Chronometer No. 141, slow, of Chicago, mean solar time, (at 10h. 47m. mean time,) 4m. 42s.14.

Rate per mean solar day, — 08.746; or per mean solar hour, — 08.03109.

Ist.-Chicago signals recorded at both stations.

Times of Signals given at

Chicago by mean solar Chronometer

No. 141.

Correct Chicago mean solar

time of Chicago signals.

Times of

Chicago Dunleith
signals as noted correct
at Dunleithsidereal time
by sidereal

of
Chronometer Chicago

No. 2557. signals.

Difference of

Longitude by Chicago each signal.

reduced Dunleith west sidereal time of the meridian of

of Chicago Chicago observing signals. station No. 3.

h. m. 8. h. m. 8. | F. m. 8. | h2 m. 8. | h. m. 8. I h. m. 8. 10 42 10 10 46 52.14 10 19 16.5 8 41 01.60 8 53 06.27 0 12 04.67 10 45 10 10 49 52.14 10 22 17 18 44 02.09 8 56 06.76 0 12 04.67 10 48 10 10 52 52.14 10 25 17.5 8 47 02.58 8 59 07.26 0 12 04.68 1st Mean.-Electric signals sent from Chicago to Dunleith, 0 12 04.673

2d.—Dunleith signals recorded at both stations.

h. m. 8. h. m. 8. h. m. 8. h. m. $. h. m. $. 1 h. m. 3. 10 28 18 10 51 10 10 55 52.14 9 02 07.75 8 50 03.06 0 12 04.69 10 31 18.5 10 54 10 10 58 52.14 9 02 08.24 8 53 03.55 0 12 04.69 10 34 19.0 10 57 10 11 01 62.159 08 08.74 8 56 04.04 0 12 04.70 10 43 20.5 11 06 10 11 10 52.15 9 17 10.22 9 05 05.51 0 12 04.71 10 46 21 11 09 10 11 13 52.15 9 20 10.71 9 08 06.00 0 12 04.71 2d Mean.--Electric signals sent from Dunleith to Chicago, 012 04.70 1st Mean.—Electric signals sent from Chicago to Dunleith,

as above, - - - - - - - - - 0 12 04.673

Result:-Dunleith Station No. 1, is west, in longitude of Chi

cago observing Station No. 3, by a mean of the two sets of
signals, - - - - - - - -

- 0 12 04.686

Longitude of Chicago observing station No. 3, west of the meridian of Greenwich,

+ 5 50 31.20

Determination 1st. Longitude of Dunleith observing station, west of the

meridian of Greenwich, - . .

6 02 35.88

For the second determination, reference must be had to the timeobservations at Dunleith, of the 22d of February; and to those at Chicago, as before stated, of the 20th and 23d of February, and to the following telegraphic signals, viz.

Determination of the difference of Longitude between Chicago and

Dunleith, Illinois, by electric signals for comparisons of time,

February 22, 1859. Sidereal Chronometer No. 2557, fast, of Dunleith sidereal time, (at 10h. 00m. sidereal time), lh. 38m. 208.51.

Rate per sidereal day, + 58.308; or per sidereal hour, + 08.221.

Mean solar Chronometer No. 141, slow, of Chicago, mean solar time, (at 12h. 01m. 42s. mean time), 4m. 42s.92.

Rate per mean solar day, - 08.746; or per mean solar hour, • 08.03109.

1st.-Chicago signals recorded at both stations.

h. m. 8. h. m. 8. Th. m. 8. h. m. 8. Th. m. 8. | h. m. 8. 11 57 00 12 01 42.92 11 38 22 10 00 01.50 10 12 05.91 0 12 04.41 12 00 00 12 04 42.92 11 41 22.5 10 03 01.99 10 15 06.40 0 12 04.41 1st Mean.--Electric signals sent from Chicago to Dunleith, 0 12 04.41

019

2d.—Dunleith signals recorded at both stations.

h. m. $. h. m. 8.
h. m. $. Th. m. 8. h. m. 8.

| h. m. 8. 11 47 23.5 12 06 00 12 10 42.93|10 21 07.39 10 09 0.97 0 12 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 22 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 2d determination
of Feb. 22d, 1859, . . . .

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

above given, . . . .

6 02 35.62

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. 35.88. 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 perfect 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 Mil. waukee, 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 Dunleith), 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 lati. lude 41° 36' 05" 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.