316 OBSERVATIONS ON THE MAGNETIC DIP, 
request the society to examine the subject so far as to understand the results at which I 
think I have arrived. Especially am I anxious that they should examine the double 
siphon curve which represents the magnetic forces along a line traversing a trappean 
or other pinnacle, capable of becoming feebly magnetic; or, the proposition may be stated, 
without reference to a figure, as follows. The intensity which ordinarily has a value 
along a line of moderate length, not varying beyond certain moderate limits, becomes, 
at the base of a trappean pinnacle extraordinarily diminished, and, at the top of the same, 
still more extraordinarily increased. ‘This, it will be seen, was decidedly the case at the 
Palisades of Fort Lee, at Snake Hill, near Bergen, and at Garret Rock of Patterson, 
New Jersey. Iam aware that before this can be admitted as a general law it must be 
verified in a greater number of instances, and, to draw attention to the settling of the 
question by the very legitimate method of multiplied observations, is the object of my 
addressing to you this note on the subject. 
JOHN LOCKE. 
SERIES FOR 1844. 
Cincinnati, March 21, 1844; Latitude 39° 06’, N.; Longitude 84° 22’, W. 
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. 
70° 28’ | 4 
5 1h.39m.028.8 P}/1851.2 |46°5 |1352.48)/1829202,1504| 997.67 
6 3 O01 59 6 {1345.6 [46 5 |1347.02,1814947.8400) 997.92 
Mean,| 997.79f} 1000.23 
Locality and geology as previously described. 
Cincinnati, July 4, 1844. 
70° 25’ | 4 9h.45m.59s.2 AJ1111.59| '76°0|1110.43/1233054.7849 
5 |10 10 59 0 {1352.4 | '76 0)1350.90)1824930.8100 
6 |10 40 44 0 {1348.0 | 78 5)1345.80|1811177.6400| 1000. 1000. 
The above is assumed as the base of this series of observations. ‘The logarithm of the 
total intensity, in the terms of the horizontal intensity, 3.4747251. 
Wheeling, Virginia, Latitude 40° 08’, N.; Longitude, 80° 47’, W.; March 24, 1844. 
1156.6 |1337723.56 Dreee| 
1410.95 1990779.9025|916.69 1012.9 
72°19'20"| 4 3h.50m.015.6°P/1156.0 | 52°0 
5 | 4 20 00 8 {1410.0 | 50 5 
Observations made in a ravine above the city. Sandstone and shale, of the coal mea- 
sures, lying nearly horizontally. 
* Some mistake in the observations. + That at Cincinnati, July 4, 1844, being 1000. 
t{ It appears that the needle No. 4 was out of level during almost the whole journey, viz., until June 20, giving 
an intensity uniformly too high. From a mean of twenty observations a subtractive constant was obtained, the 
multiplier for which is .00285. Then, 922.58 — 922.58 x .00285 = 919.95, which is still much higher than 
the indication by No. 5, upon which I rely with so much more confidence that I have excluded the result by No. 4. 
