370 A. D. Bache on a Magnetic Survey of Pennsylvania 
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Group I. es 
Philadelphia,* 18420 4166 0°000 4:166 
Doylestown, 1841-6 4189 —0'001 4188 
Easton 1841-6 4121 —o'00I 4120 
Reading, 1840-6 4000 —0-00 ag 
Frenchtown, 1840-6 4:312 —0'004 4:308 
Baltimore,* 18406 4265 0-00. 4-261 
Washington, 1843-0 4:320 +0:003 4-323 
, 1840°6 4:078 —0-004 
Duncan’s Isl 1840°6 3-963 0:00 3-959 
Near Mercersburg,* 40°6 4-188 -—o0'004 | 4184 
Mean,| 4:158 
Group II 
Armagh, 1840'6 4:038 —0'004 4°034 
Frostburg, 1840°6 4:298 —0'004 42 
N 1840°6 4207 -0°004 4:203 
Near Pittsburg, 1840°6 4-04 —0'004 4:045 
conomy, 1840°6 | 4-00 0-004 | 4:004 
Wheeling, 1840°6 4-053 -0°004 ie” 
Steubenville, 1840.6 3-947 -0°004 — 3943 
Mean,| 4082 
Group IIL. 
arren, 1841'°6 3-978 -o'001 3977 
Mercer,* 18416 4-000 -o'001 999 
Ashtabula, 1841'6 3-838 0-001 3-837 
a aN 1841'6 3-71 0-00! 3-791 
Dunki 18416 3-621 —O'001 3-620 
Plioottevitle,® 15416 3-726 —0°001 3-725 
Berlin’s Tavern, 1841°6 4:026 =0'001 £025 
Mean,| 3853 [ 
Group IV. 
Curwinsville,* 18416 3: -o'00r 998 
Belvidere, 1841°6 3: —o'001 : 
Bath,* 18416 677 | -o-00L 676 
Owego, 1841-6 614 -0'001 ‘613 
Silver Lake,* 1841°7 782 0°00] 781 
Wilkes: che 33 —0'001 =. 
Williamsport,* 1841-6 * -o-00! : 
ee 1841-6 | 4-069 -0-001 4-068 
18406 | 3-984 | -o-oo4 | 4 ye 
ae ber 18406 | 4109 | -o-004 | 410. 
Mean, | 3883 
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Niagara Palla, 3-565 | +0005 | 3570 | 
Toronto Ob.,* 18436 | 3537 | +0005 | 3542 : 
Rochester, 3-560 | +0005 | 3:56 3 
eneva,* 18437 | 3635 | +0:005 | 3640 | 
Syracuse,* 18436 | 3556 | +0005 | 3-561 | 
Oswego, 18436 | 3467 | +0005 | 3:472_ S 
Mean, 3-558 ; : = 
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