332 
OBSERVATIONS ON THE MAGNETIC DIP AND DECLINATION. 
mouth of Mississippi River. 
AND SIMMS, OF LONDON. 
Latitude 28° 58’ 
I. OBSERVATIONS FOR THE DIP OF THE MAGNETIC NEEDLE, WITH INSTRUMENT BY TROUGHTON 
Date and place of observation.—1840, January 29th. At the Light-House, South-West pass, 
50”, N.; Longitude 89° 21’ 27”, W. 
ad of | Polarity of | Face of Tat atekte Mean solar time| North end of Needle|South end of Needle} Mean of both ends] Attached Name 
Needle. ont Instrument.| of Needle, | Of observation. reads of needle. Thermometer. 
| of Needle. H. M, Deg.|Mins.gT ‘enths.|Deg.|Mins.f’Tenths. Deg.|Mins.&Tenths, (Fahrenheit,) |Observer, 
lid N E E | 11.00a.m./59.08.0 |58.48.0 |58.58.0 67°. |J.D.G. 
his 66 WwW W cla 58.00.0 58 .20.0 58 .10.0 
ie 6 W E 6 66 58.50.90 569.12.0 59.01.90 
G s te E WwW 667 2S 58...52..0 58... 30 -O (58 r 41.0 
1 Ss | SE 9.40 Pum.|08.. 62.0  (58.40.0-. [58 46.0 | . Jf, D.G. 
7 - WwW W 58. 30.0 58 .42.0 58.36.0 
6 “ W E 4.05 67.15. 0 57.35. 0 67 «25:50 
“ 6 i ‘W 4.05 60. 52.0 60.15. oO 60 .«°33...5 
Needle No. 1, with marked end north, gives . 68° 42°56 
Needle No. 1, with marked end south, gives 58 50.12 
Dip, by sixteen observations on needle No. 1, 58 46.3 
2 s WwW WwW 4.30P.m./57.40.0  (57.15.0 [57.27.56 66°. J.D.G. 
} iy E E 58 . 30.0 58. 35.0 08 ..32.5 
6 6 E WwW 57.107. 0 57. 85.0 57 522.5 
p« fo Wife Bak 68.30.0 |58.17.0 |58.23.5 
bo@ch.oN W WwW 58.35.0 (58.15.0 |58.25.0 J.D.G; 
oe E E 59.35.0 |59.80.0 |59.382.5 
| wil “ E Ww 59.45.0 (59-23.0 |59.34.0 
| « «“ Ww E 59.57.0 (|59.40.0 |59.48.5 
Needle No. 2, gives, with marked end north, : 59° 20’ 
With teat end south, ; ; ; . 57 56.5 
Dip, by sixteen observations on nies No. 2, 58 38 .25 
Dip, by sixteen observations on needle No.1, . 58 46.3 
Magnetic dip, at the Light-House of the South-West pass of the ‘Missise! ppl, 
DOS 42725 
by a mean thirty-two observations on both needles, . 
Nore.—The position chosen for the observations was about four hundred feet south-east of the new light- 
house, on Backus Island, which had been finished within a few days previous to these observations. 
Il. OBSERVATIONS FOR THE DIP OF THE MAGNETIC NEEDLE. 
Date and place of observation.—1840, February 11th, at Dr. Everett’s house, west bank 
of Sabine River, near its entrance into the sea; Texas. 
Longitude 93° 51’ 30”, west of Greenwich. 
Norr —The point of msec of the magnetic dip bears, compared with the true meridian, north by west, 
2 Pp. W., and is distant ie 
Sabine, 
guns 
Latitude 29° 43’ 54”, N.; 
3 miles from mound A, which marks the western shore of the mouth of the river 
= 
1D 
WwW 
i 
11.35 a.m./59.15.0  (59.00.0 (59.07.5 — 
026 may 2.0 °° «(67.87.0 «675 81.0 
0.50 59.00.0 |59.15.0 |59.07.5 
1.20 58.20.0 |58.05.0 (|58.12.5 
in the maps abane “the demarcation of the boundary between the United States and ‘Texas. 
