318 OBSERVATIONS ON THE MAGNETIC DIP, 
Washington, between the War Office and the President’s house, April 11, 1844. 
Duration Calculated 
| 
Dip. | No.of | Epoch of commencing | of 500 |Tempe-| duration Square of the | Horizontal] Total intensity, 
\Needle. Vibrations. Vibrations.| rature.| at 60°. Preceding. intensity. |Hor. being 1000, 
| 
71°20'30"| 4 10h A8m.015.2 P/1141,.20'78° 0 |1139.87/1299303.6169/949.71 
5 {11 13 00 0 |1390.00'79 00)1388.06)1926710.5636/947.16 
6 (11 46 02 4 |1384,80/84 00,1381.88)1909592.3344/948.47 
- Mean,|947.81 993.00 
This station, approaching to those of the Observatory and Depot, exhibits a correspon- 
dent approach in the elements. 
Georgetown, a little east of the point at which High Street crosses the first ridge after leaving the city, in an 
enclosed wood; April 10, 1844. 
71°19'00"| 4 | 1h.49m.59s.6 P|1144.8 | 75°0|1143.801308278.44 |943.19_ 
5 | 2 14 08 6 1394.00) 73 5,1392.60 1939334.76 941.07 
6 | 2 45 00 0 |1888.80] 75 0,1887.00)1923769.00 (941.47 
| Mean,|941.27 | 984.88 
Substratum, a light micaceous, ferruginous soil, superimposed on gneiss rock, extremely 
prone to disintegration, from a loss of its feldspar. 
Mount Vernon, Virginia, Latitude 38° 41’; Longitude 77° 07’; April 11, 1844, about seven hundred feet westward 
from Washington’s tomb. 
1126.80 
1375.20 
| 84°0 
86 0 
1125.04|1265715.0016|974.91 
1372.70|1884305.29001968.49 | 993.30 
70°55'30"| 4 112h.43m.03s.6 P 
5 1 13 O1 2 
Probably the eocene tertiary, superimposed on gneiss. ‘The experiments were made 
in the shadow of the trunk of a pine tree. 
Philadelphia, Latitude 39° 57’, N.; Longitude 75° 10’, W.; April 19, 1844. In the yard of the Magnetical 
Observatory, near Girard College. 
71°59'15"| 4 9h.52m.00s. 1158.40} 51°0/1158.92/1343095.5664|918.07 
5 10 28 00 4 |1412.00) 52 5)/1412.74)1995438.7600/914.55 
6 |10 59 O1 6 {1406.40 55 |1407.02)1979311.3344/915.55 
| Mean,|915.05 | 991.84 
The above is an unusual result at Philadelphia, the total intensity having been usually 
between 993 and 995. Iam unable to account for this, unless it has been the result of 
using a chronometer, the rate of which, in various positions, had not been well determined, 
my own chronometer having been broken. 
Princeton, New Jersey, Latitude 40° 22, N.; Longitude 74° 39’, W.; May 23, 1844; at the usual locality, 
shown to me by Professor Henry. 
72°40'15"| 4 | 4h.05.035.2 P1182.8 | 77° [1181.5 |1395942.25 [883.30 | 993.96 
Shale stratified nearly horizontally. This locality is in the open field. 
Princeton, second station, Potts’s Woods, May 23, 1844. 
72°41/25"| 5 | 5h.42m.018.6 P|1438.4 | 72°0 [1437.2 |2065543.84 [883.51 | 994.9 
At this station the instruments were more perfectly sheltered from the sun. Geology 
same as above. Materials believed to be not magnetic. 
