292 OBSERVATIONS ON THE MAGNETIC DIP, 
this neighbourhood. The experiments were made on the margin of the creek, under 
the shadow of a shelving rock, which, being about nine feet high, served to screen the 
apparatus from the sun. The table land undulating, fertile, grassy prairie. 
11. White Water, (lowa,) Latitude 42° 18’, N.; Longitude 90° 51’, W.; October 18, 1839.. 
Duration Calculated Total intensity, 
Dip. No. of | Epoch of commencing 
of 500 | 'Tempe-| duration Square of the Horizontal|Total intensity, |that at Cincin- 
Needle. Vibrations. Vibrations.|rature, at 60° preceding, intensity.| Hor. being 1000.|nati being 1000. 
72° 55’ | 3 |11h.04m.005,4 1308.8 l77°5 |1307.47/1709477.8009 | 892.70 3038.85 1016.53 
Declination, 9° 10’, east, (surveyors. ) 
Locality, in the sandy channel of a dried up brook, beside a limestone bluff. 
12. North Branch of Makoqueta, Latitude 42° 23’, N.; Longitude 91° 09’, W.; October 9, 1839. 
72° 51 | 3 |11h.59m.59s.6 A| 13096. | 59° |1309,.67|1715235.5089| 889.71| 3017.25 | 1009.31 
Declination, 9° 35’, east, (surveyors. ) 
Cloudy and interruptedly rainy, with gusts of wind from the south. Observations 
made inside of the tent. Dipping needle fluctuating, as if by an aurora or a “ magnetical 
storm.” 
13, Dubuque, (Lowa,) Latitude 42° 29’, N.; Longitude 90° 39’, W.; October 14, 1839. 
73° 05' | 3 j12h.51m.03s.6 P| 1316. | 54° |1316,46|1733066.9316| 880.55| 3028.66 | 1013.00 
Declination, 8° 22’, east, (surveyors.) 
At Dubuque’s grave, one mile distant from this locality, the dip is 73° 05’ 45”. The 
dip and intensity, as first given, were taken in the bottom of Dougherty’s Lead mine, 
one hundred feet deep; both the dip and intensity appeared to be the same as at 
Dubuque’s grave, a locality about a mile distant, and immediately on the river bank. 
The lead mine is a vertical fissure in the limestone, from three to twelve feet wide, run- 
ning from east to west, and but partially worked out. It would not seem, then, that these 
veins of Galena exert any sensible influence on the magnetic elements. 
14, Forks of Little Makoqueta, (Lowa,) Latitude 42° 31’, N.; Longitude 90° 47’, W.; October 20, 1839. 
73° 08" | 
1 | 64,15m.04s. A\ 1634, | 34° [1639.4 |2687632.36 | 880.88 
| 2 17 02 04 4 |1612. | 36 |1616.16/2611973.1456| 884.31 
| 8 | 8 16 00 4 | 1817. | 51 3/1317.86|1736754.9796| 878.61 
| Mean,| 881.27] 3037.34 | 1016.02 
Declination, 8° 30’, east, (surveyors.) 
Clear, brisk north wind. Experiments made inside of the tent, all iron being removed. 
Locality, the diluvial bottom of a small stream, having perpendicular bluffs of horizontal 
cliff limestone, two hundred feet high, on each side, and distant, say four hundred yards, 
15. Turkey River, (lowa,) Latitude 42° 42’, N.; Longitude 91° 05’, W.; October 22, 1839, 
73°11’ | 3 |10h.11m.04s.8 |1322.4| 65° [1822. |1747684. | 873.19] 3018,18 | 1009.61 
Declination, 9° 00’, east, (surveyors. ) 
