AND THE INTENSITY OF MAGNETICAL FORCE. 295 
26. Mason, Ohio, Latitude 39° 22’, N.; Longitude, 84° 13’, W.; August 25, 1840. 
re ae si Duration Calculated | | Total intensity, 
Dip. No. of | Epoch of commencing} of 500 |Tempe-| duration Square ofthe | Horizontal Total intensity,|that at Cincin- 
‘Needle, Vibrations. Vibrations.| rature. | at 60°. preceding. aiid ai being 1000.|nati being 1000. 
| 
70°54'12") 1 9h.80m.00s. AJ1557.6 | 75° |1554.8 | 241'7403.04 | 979.35 
2 {10 11 O02 8 |1543.2 | 77 (1589.4 | 2369752.36 | 974.69 
3 j10 51 04 4 {1251.2 | 78 1249.9 | 1562250.01 | 976.83 
Mean,| 976.90] 2986.16 998.90 
Calm, cloudless, fine. Locality, in the woods, on the level surface of the blue lime- 
stone. 
27. Cincinnati, August 26, 1840, 
70°27'54”/ 1 |11h.4 m.59s.6 A) 1542.8 (74° 4 |1540.14/2372011.2196 | 998.10 
2 jll 40 04 8 | 1526.8/75 5 |1523.37)2320656.1569 | 995.32 
3 112 16 O1 2 | 1238.0)76 5 |1236.82/1529723.7124 | 997.67 
Mean,| 997.03} 2981.74 997.43 
Calm, sun shining, but through a hazy cloud. 
It appears above, that although the total intensity at Mason, August 25, was less than 
the same at Cincinnati, August 18, yet it was greater than at the same place on the 26th. 
As this experiment was made on the day succeeding that at Mason, it may be taken as 
the nearest correct comparison. 
28. Williamstown, Kentucky, Latitude 38° 36’, N.; Longitude 84° 22’, W.; September 1, 1840. 
70°04'07"| 1 |10h.32m.59s.2 A/1532.4 | 77° |1529.27/2338666.7329| 1012.3 
2 jill 238 #13 2 (1514.8 | 77 |1511.07/2283332.5449/ 1011.1 
3 {12 06 O1 4P)1228.6 | 79 |1227.25)1506142.5625) 1013.2 
Mean,| 1012.2 2969.27 993.25 
Locality, about half a mile east of Williamstown, on a ridge bordering a ravine. 
Rocks, blue fossiliferous limestone, underlying the soil. The greatest eastern elongation 
of polaris had for its azimuth 2° 57’, west of magnetic north. The variation or declina- 
tion was then about 4° 57’, east. This was ascertained by the usual method adopted 
by surveyors, by means of plumb lines. 
29. Lexington, Kentucky, Latitude 38° 06’, N.; Longitude 84° 18’, W.; September 2, 1840. 
69°54'30"| 1 4h.17m.108.4 P}1531.2 | 74° 1528.63 
2 4 54 02 4 {1514.4 | 73 1511.56 
3 5. 30 00 1228.8 | 71 1228.09 
| 
2336709.6769 1013.22 
2284813.6336 1010.93 
1508205.0481/1011.84 
Mean,1012.00, 2945.94 | 985.42 
Weather cloudy. Locality, Richard Higgins’s garden. Substratum, horizontal lime- 
stone, covered by a soil about nine feet deep. ‘This is probably identical with the lime- 
stone of Cincinnati, but is more massive, containing less clay marl, which abounds at 
Cincinnati, interstratified with the thin layers of stone. 
30. Clay’s Ferry, Latitude 37° 54’, N.; Longitude 84° 18’, W.; September 3, 1840. 
G9° 49’ | 1 |12h,.20m.05s.2 P| 1526. | 75° 5/1523.25] 2320290.5625|1020.35] 2957.82 | 989.27 
On the bank of the Kentucky river. Substratum limestone, the same as at Lexington. 
A bluff limestone bank within one-third of a mile. 
VOL. IX.—78 
