AND THE INTENSITY OF MAGNETICAL FORCE. 323 
The following diagram shows the curves of dip and intensity in traversing Snake Hill 
from west to east, as indicated by the above results, and by experiments at neighbouring 
localities. 
&d 
a & 
A : 
a» | SNAKE HILL. i 
OF 
73, 00 
Fort ee about nine miles north of New York, on the west side of the sine tien — 2, 1844. 
‘Duration | Calculated ‘Total inte nsity, ‘ 
Dip. No.of |Epoch of commencing] of 500 |Tempe-| duration Square of the Horizontal |that at Cincin- 
Needle. Vibrations, Vibrations, rature.| at 60°, preceding. intensity. jnati being 1000. 
72°28’ | 4 | 4h.84m.02s.4 P| 1182.2] 66°5 | 1181.7] 1396414.89 | 883.02 | 982.43 
Fort Lee was situated on a promontory which forms the southern termination of the 
palisades. ‘This promontory has the Hudson river on the east side of it, a ravine and 
rivulet on the west, and a valley, or recess on the south, in which is situated the village 
called “ Fort Lee.” 
The palisades are of trap rock, somewhat basaltic or columnar in structure, but present- 
ing rather vertical plates than polygonal columns. Beneath this basalt, at Fort Lee, is 
a bed of sandstone and shale, lying in a very slight inclination. The valley of the vil- 
lage exhibits a deep deposite of sand and gravel, apparently not magnetic. The station 
of “the orchard” was of this kind. The above, or station No. 1, was on the ridge of the 
palisades, about one-third of a mile north of, or above the promontory. The rocks were 
of trap, scarcely covered with soil, and supporting dwarf cedars and pines. 
Fort Lee, Station No. 2, May 8, 1844. 
Near the lower end of the promontory, and at the verge overlooking the precipitous 
descent to the Hudson. With the dipping compass standing on the rocks, the dip read 
73° 07'; but when raised up, say three anda half feet on the stand, it read as in the 
margin below. 
72°47'00" | 4 | 6h.12m.038.6A | 1186.4 | 65°O | 1186.02 | 1406596.0000 | 878.00 | 994.26 — 
Rocks naked, and consisting of massive vertical plates. 
Fort Lee, Station No, 8, about forty feet south of No. 2, and on the immediate southern verge of the precipice ; 
May 3, 1844. iia 
72° 51’ | 4 | 64.56.0254 A | 1167.6 | 70° | 1166.85 | 1861538.9225 | 905.63 | 1029.82 
VOL. IX.—85 
