-— —  ? = 
a 
150 Terrestrial Magnetism. 
tained by the two needles seldom differed more than one gninute, 
I deem it essential to correct the error by copying below the en- 
tire minutes of the observation at that place. 
Davenport, Iowa Territory, Sept. 15, 1839. Lat. 41° 30! N., Lon. 90° 18! W. 
| Needle No. 1. B North. ° Needle No. 2. B North. 
Face of in-| Face of Face of in-; Face of 
strument. | needle. Dip indicated. strument.| needle. Dip indicated. 
= : 2°55! E E. 1°58’ 
w. w 70 47 w w. 72 02 
w E 72 A7 Ww E. 71 54 
E : ~~ FY 06 E w. 72 03 
A North. A North 
E E. 70 59 E E. 2 16 
w w. 72 52 w w. 71 26 
w E. 70 53 w E. 72 12.5 
E w. 72 57 r. | w. 71 28.5 
8)575 16 8)575 20 
Mean, 71 54.5 ; Mean, 71 55 ___| 
I will here add some observations made on the dip in Ohio, 
Indiana and Kentucky, within the last three months. The re- 
gion over which these observations have been extended, embra- 
ces rather more than two degrees of latitude and three degrees of 
longitude. Dip, intensity, and declination, were all made the 
objects of inquiry, but I here communicate only what relates t 
the dip, especially to show the close agreement of the results of 
the two different needles. : 
No. 1. Piqua, Ohio, Lat. 40° 06! N.,,Lon. 84° 10! W. Aug. 22, 1849. 
TI Néédle No. 1. A North. Needle No.9. B Noth. 
Face of in-; Face of | a of in-+~ Face of ee 
strument. | needle. Dip indicated. strument.| needle. __Dip indicated_ 
E. E. 70°40’ E. E. 71°47’ 
w. w. 72 34 w. 71 33.5 
w. E. 70 43 Ww E. 71 46 
E. w. 72 30 E w. 71 31.5 
B North. A North 
E. E. 72 44 E E. 71 38.5 
w. w. 70 33.5 w w. 71 23.5 
w. E. 72 42 w E. 71 39.5 
E. w. 70 24 E. Ww. 71 Bo, 
8)572 50.5 ~8)572 43 
Mean, 71 36:31 Mean, 71 35.375 | 
