re) 
<a) 
~ 
AND THE INTENSITY OF MAGNETICAL FORCE. 
36. Vincennes, Indiana, Latitude 38° 43’, N.; Longitude 87° 25’, W.; ee 18, 1840. 
Duration 
Dip. |e et Za _— of commencing) of 500 
— Vibrations. Vibrations, 
| Cale ulated | 
dur 
he ai. Total intensity, 
on 
at 60°. 
Horizontal | Total intensity, |that at Cincin- 
intensity. as being 1000. jnati being 1000. 
| 
| 
69°51'10" 1 |10h.12m.028.4 A}1517.6 58°5 |1517.862303929.3369 1027.56. 
| 2 j11 06 03 6 [1502.0 60 5 |1501.9 2255703.61 [1024.25 | 
| 3 |ll 46 04 % 5 |1219.42 1486985.1364)1026.28 
| 
Mean,|1026.03, 2978.89 | 998.54 
Clear, calm, wind westward, Locality, bank of the Wabash river, one and one- fourth 
miles above Vincennes. Soil, alluvial substratum sandstone, of the Illinois coal basin. 
Tempe- 
rature, 
Square of the 
preceding. 
37. Paoli, Indiana, Latitude 38° 35’, N.; Longitude 86° 25’, W.; on mene 20, 1840. 
1 71° |1515.2 (2295831.04 |1031.22| 
2 110 44 00 1499.6 | 73 |1496.'77/2240320.4829)1031.01) 
3 j11 31 58 4 |1216.4 | 76 1215.27|1476881.1729) 1033.30! 
| | Mean,|1031.84; 2953.68 | 988.04 
69°33'47” [10/.0577.008.4 AJL517.2 
One-fourth of a mile north-east of the court house, on a side hill. Substratum, com- 
pact horizontal limestone, (the carboniferous.) Clear, calm, very fine; wind north-west. 
38, Cincinnati, September 2 24, 1840. 
70°29'11"| 1. {112,19m.008.6 Al1542.8 66° 4)1541.8 2377147 24. | 995.94 
2 112 00 08 8 P/1524.6 |70 {1522.4 |2317701.76 | 996.58 | 
3 j12 89 OL 2 {1237.2 (70 |1236.5 |1528982.25 . | 
Mean,| 996.88} 2984.40 | 998.31 
Latitude and locality as before described, 
IV. SERIES, 1841, CINCINNATI TO NEW YORK. 
39. Total intensity at Cincinnati, May 8, 1841, compared with that at the same place, August 18, 1841, the las: 
being reckoned unity. 
70°26'11"] 1 |11A.44m.008.4 [1539.6 159° 17/1539.62 2370368.16 | | 
2 12 17 00 4 |1520. (61 4 [1519.69 2309457, 6961 1000.01) 
S12 27 06 6 -11286.. 62 1235. 86. 1527349. 9¢ 396) 999.16 
4 1 12 02 8 1110.4 (62 1110. 26 1232677. 2676, 
5 I 86 00°8 |13860.8 (68 1350. 52,1823904. 2704! | 
6 2 08 O1 2 11847.2 '63 1346.84, 181 3977.9866. | 
Mean of the horizontal intensity by the needles Nos. 2 and 3, 999.58 2983,88 | 998.56 
After obtaining the horizontal intensities, as above, by dividing the squares of the 
duration of five hundred vibrations at any place into similar squares at the place assumed 
as the standard of unity, the reductions for total intensity were effected by the following 
formule, always using Hassler’s logarithmic and trigonometric tables, as published in 
New York, in 1830. 
As cos,70°26'11” 9,5248544, Magnetic dip at Cincinnati, May 8, 1841, 
Is to R, 10. Logarithmic radius. 
So is 9.9956  0,9998176 Hor. Int. at Cincinnati, May 8, that at the same place Aug- 15, 1840, being 10. 
To 29.8513 1.4749632* Total intensity, May 8, horizontal intensity, August 18, 1840, being 10. 
* 1. 4751458, Log. of total j intensity, - hetiactilal beling unity. 
