322 OBSERVATIONS ON THE MAGNETIC DIP, 
Warren, Ohio, Latitude 41° 16’, N.; Longitude 80° 55’, W.; June 25, 1844. 
| Duration Calculated ‘Total intensity, ; 
Dip No. of | Epoch of commencing] of 500 | 'Tempe-| duration Square ofthe  |Horizontal |that at Cincin- 
Needle. Vibrations. VAN EAONS, |TBURIY. at 60°. preceding. Intensity. |nati being 1000. 
; 
72°55/52"| 4 8h.53m.028.8 A|1184,80/77°5 |1183.47|1400601.2409 1880.35 
1440.70 81 50 
1437.60.82 00 
o 22°00 8 
9256 60-0 
1438.59 
1434.84 
5 
6 
206951.11881 [881.81 
2058765.8256 |879.74 
_ Mean,|880.63 | 1005.60 
In a wood, and a little west of the bridge. Alluvium, superimposed on the shale of 
the coal formation. 
Wellsville, Ohio River, Latitude 40° 38’, N.; Longitude 80° 44', W.; June 26, 1844. 
72°35'20" 
4 8h.16m.595.6 A|1196.4 |83°0 |1194.60 1427069.16 |Erroneous. 
5 9 44 00 0 {1482.4 185 0 |1429.90/2044614.01 (892.55 
6 |10 10 00 4 |1427.2 |85 0 |1424.33/2028715.9489\892.77 
Mean,892.66 | 999.91 
On the deep alluvium of the Ohio river, in a dark, shady wood. Surrounding hills, 
shale and coal. 
The following observations were intended expressly to show the effects of local attrac- 
tions, especially those occasioned by pinnacles of trap rocks, 
Snake Hill, near the top, April 30, 1844; Latitude 40° 44’, N.; Longitude 74° 08’, W. 
73°12/'26"| 4 |12h.47m.03s, 1194.8 | 75° 
6 | 1 78 
1193.07|1424919.69 1865.35 
2 09 05 2 {1450.0 144'7.70|2095835.29 |864.18 
1002.72 
Snake Hill is an outlier of trap about seven miles westward from New York, 
rising abruptly from the salt marsh which nearly surrounds it. Height, two to three 
hundred feet. It is a prominent object, and was one of the stations in the coast survey. 
The local effects are sufficiently apparent. The dip, in unexceptionable situations near, 
would have been about 72° 45’, and the intensity 993 or 4. 
Snake Hill, west side, close to the bottom of the perpendicular rock ; April 30, 1844, 
883.24 
—2,52 
880.721 987.06 
Now if we suppose the vertical trappean hill to be a magnet by terrestrial induction, 
the upper end must possess an intensity higher than is due to the locality, while the 
lower end, or bottom of the hill, must exhibit a magnetic force below the same point. 
In the present case, the mean of the two, the one at the top and the other at the bottom 
of the hill, viz., 994.88, tallies well with the force or intensity indicated at localities in 
the neighbourhood, where there is no cause of local disturbance, as at Columbia College, 
994.35, or at Princeton, 994.82. 
Snake Hill, south-east side, April 30, 1844. 
72°27'22" | 4 | 5h.50m.003.8P | 1172.0 | 65°0 | 1171.60 | 1372446,56 1898.43 
—2.56 
895.87 
996.19 
This observation was made on the level of the marsh, and a few rods distant from even 
the talus, or rocks tumbled from the precipice. 
