‘= Ss , 
£ Pe at 
e 
86 © MogneioD Dip in in the United States. — 
gitudes have all been ‘diminished seven minutes, which bt my 
observations is the error in the assigned longitude of Hudson. 
Column fourth exhibits’ the observed dip, reduced to Jan. 1, 1840, 
by assu the annual motion to be —1’.8. ‘Adopting for the 
central position lat. 41° 22/, lon. 84° 54’, we obtain the differen- 
ces of latitude and.longitude which furnish us the annexed equa- 
tions of condition. , 
Longi- |Dip,Jan. Diff. of observ’d) 
Stations. Latitude.| tude. | 1, 1840. | Equations of condition. | & comp’d dip. 
/ 
Louisville, 18x. 37 028=5 -1842- 33.7y, +17. 
t. Louis, 37 1 §| 5136 ~1652-247.7y|. + 2. 
Cincinnati, 6 \g4 2 al1.580=3 1367+ 24.1y|  — 1. 
ton, ) 46 827 =5 — 962+ + 5: 
Springfield, 55 4 24.32.405=5 - 872+ 55.2y| — 1. 
lumbus, ) 57 5 1.8)2.030 =5 - 852+ 88.9 ~30. 
anna, ) 33 812.597 =6 - 772+ 57. +1. 
Tallmadge, ' 2 50.6/3.843 =d — 1624156.7y) + 5. 
indham, ] 4.6/4.077 =5 +173.7y| + 9. 
ne ] 963 =5 - 166. + 34 
eetsbor ‘ 902=3- 72+160.9y} + 5 
banded ‘ B47=5- 7x41564y) — 2 
arren, ) 4 0382=5- G624+184.2y) + 3. 
Hartford, ys 4.017=8- Qx+195.2y| = 2. 
Bazetta, ) 4 4.015=5- 2x+187.0 - 12 
Aurora, ) 56.7|3.945=5- 22+160.7y, —- 1. 
Twinsburgh, ) 26 2.513.875 =9- Qt - 4. 
dford, 32 59.3/3.988=5+ Qr+1515y) -— . 
Kinsman rt A55=5+ Grt1948y| - 12 
Davenport, 2 52.912.882=9+ Gr-255. = 6: 
Sandusky, 4 '3.943=9+ 7+4100.4y 0.0 
Cleveland 42 4.317=9+ 8r+1438y| 414.7 
aumee, 3 32 3.798 =5+ 127+ 61.4y| —- 7.0 
Lost Grove, ) 3.032 =9 + 17x-235.4 ~10.7 
Toledo 4 32 9/4.082=6+ 192+ 66.5y) + 2.9 
Wapsipinnicon, 4 ) 2 3.240=5+ 230-245.4y 2.0 
Monr E 3 2 1/4.518=6+ 3324 69.9y| +161 
Shown | Settlement, aa ) 348=5+ 427-273.2y| —- 8.1 
armer’s Creek, i ; 32.7/3.545=6+ 512-243.6 9.0 
Ypsilanti, 14 4 16.8)}4.280 =4 z+ 60.7 -13.8 
ahoqueta, 14 43.1|3.718 =9 + 527-268.8y| + 4.4 
Ann Arbor, 18 j 12.7\4.212=0+4 56z+ 569y| -20.8 
Detroit, 19 |82 56 41.4|4.690=5+ 572+ 87.2y/ + 22 
Dubuque 29 j 4.077 =9 + 672-244.8y| + 8.7 
Mineral Point, 52 (89 58 20.3/4.338=5 + 902-222. 8y, + A 
Blue Mounds, ] eo; 6|4.677 =5 + 992-199.6 + 9.1 
Prairie du Chien, 4 91 0 16.3/4.272=5 +102z-267.4y|  —_7.3 
; 5 |89 6 3.215.053 =5 +103a-184.0y} +25.6 
The preceding equations furnish us, by the method of minimum 
squares, with the following values: 6 =3.5747, r= + .01491, 
y= -+.00262, and the direction of the isoclinal line is from \: 
80° 1’ W. to S. 80° 1’ E. Computing from these data the dip 
at the several stations, we obtain the differences given in the last 
column above. When the observed dip is greater than the com 
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