342 OBSERVATIONS ON THE MAGNETIC DIP AND DECLINATION. 
Neep.e No. 1. 
Polarity of No. of Time of 
Marked end of Needle. Readings, Observation. 
N 8 
s 8 3h. P.M. 
Dip by sixteen observations on needle No. 1, 
Dip observed, 
61° 26'.25 
61° 05’.62 
61° 15'.9 
The day was clear and very hot, with a gentle north-west wind all day. 
There was not time to observe on needle No. 2 before the hour appointed for the 
steam-boat to depart, in which I was to descend the Red river. 
IX. OBSERVATIONS FOR THE DIP OF THE MAGNETIC NEEDLE. 
Date and place of observation.—1840, August 24th—At West Point, New York. 
Latitude 41° 23’ 35”, N.; Longitude 74° 01’ W. The observations were made under 
a tent on the plain, about one hundred yards west of Execution Hollow, and remote 
from the batteries of artillery and other visible causes of local attraction. 
Weather clear, with a fresh breeze from the north. 
No. of | Polarity of | Face of |Markedside|Mean solartime| North end of Needle/South end of Needle} Mean of both ends Attached Name 
Needle. Marked end|Instrument.| of Needle, [of observation.| _ reas} | _tea |__of Needle. 'Thermometer.| of 
| of Needle. | H, M. Deg.|Mins.fTenths,|Deg,|Mins §'Tenths,|Deg.|Mins.§Tenths. (Fahrenheit.) | Observer, 
‘6 Low | W | 7.40a.m.i72. 05 72.25 72.15 J.D.G. 
aS ee ae E 8.11 74. 36 74 . 20 74 . 28 
wile varia ay | Ww | 9.00 |e. 42 72 . 22 72. 32 
«| « | w |] EB | 10.30" 3.25 73.46 —*|73.. 35.5 
Ses | Ww “Ws| 11.30 a.m.|73 . 58 74 . 30 ne ee ue 
«“ lak E 11.48 72. 33 72.16 72. 24.5 
«“ «“ | i Ww 0.15 p.m.'74 . 30 74.07 74. 18.5 
ie PO WwW E 0.40 |72,22 72. 45 72 . 33.5 
Needle No. 1, with marked end south, gives. ia 120 
Needle No. 1, with marked end north, gives To ee 6 
Dip, by sixteen observations on needle No. 1, 0 17.0 
(i. eS oe WC Bae Be. TO 78 . 45 at * Se? ee ee 
e eo} Bo poR | 3.27168. 33 68 . 05 68. 19 | 
vais icmiediied Uc uke ih oa ie eee cat 78 . 00 78.11 | 
Mehl ® pike: Witosk | B68 60008 68 . 22 68 . 12.5 | 
21N 4 .W | W f°4.05 2.068. 46 69 . 03 68 . 54 
“ aE 7 Be Sees et or 78.15 8 . 26 | 
® Po @ obs Bol bo We beet ¢ 685, 55 68 . 30 68 . 42.5 | 
«“ ee | | E | 4,25 77 , 60 78.15 (78. 05 
Needle No. 2, with marked end south, gives, 
Needle No. 2, with marked end north, . 
Dip, by sixteen observations on needle No. 2, 
A direct mean between the results of No. 1 and No. 2 is, 
By giving twice the weight to No. 1 which is given to No. 2, the dip will be, 
73° 18'.75 
73 31'.87 
73 25.06 
70 Sli 
73° 20'.09 
Nore.—This is the last observation ever made with needle No. 2. It was broken, a few days afterwards in 
an attempt to correct it of the warp which oceurred from the accident described at page 339, ‘J 
were subsequently made for this instrament by Mr. J. N, Baur, a very ingenious mec} 
They are designated as No, 3 and 4 in the observations which follow, and proved to be remarl 
2 
wo other needles 
vanie of New York. 
kably good needles, 
