and parts of adjacent States. 367 
d | Diff. 
i er nes ee 
° 
I 72°47 72°54 -o 
71°73 71°68 +0'05 
iL 72°20 F211 +0°09 
Vv 73°20 73-31 -o'll 
72°54 72°61 -0'07 
VI. 74:56 74-47 +0°09 
VIL. 73-50 73°51 -O'0L 
VIIL 74°74 74-76 -0'02 
TX. 74°31 74-26 +0°05 
The isoclinal lines ae 71°, 72° 78°, 74° and 75° pass through 
the following positio 
aP; ae i le 
Lat. 9 
72°, Long. 75 00 78° 00’ 81° 007 
Lat. 39 49 39 59 40 10 
78°, Long. 74 00 78 00 81 00 
Lat. 40 50 41 05 41 15 
74°, Long. 74 00 78 00 81 00 
Lat. 41 57 42 11 42 22 
75°, Long. 75 00 77 00 79 00 
Lat. 43 07 43 18 43 20 
‘These lines have been finally adopted. 
Comparison of the observed and computed dip. 
Observed Computed Diff. observed 
Dip Dip. computed. 
Grou Jy é ° ° 
New pers 72°66 72°93 0°27 
Easton,** 72°65 72 —o'15 
72°64 72°51 +013 
Doylestown, * 2-39 72°44 -~0'05 
eading,* 72°54 72°42 +0°12 
Philadelphia, |. arg 72°14 -o1g 
oup * 
Frenchtown,* 71°67 71°75 -0'08 
Baltimore, 91°57 71°45 +4012 
W 71°26 71-06 +0°20 
Harrisburg, 72°34 72°32 40°02 
Near Mercersburg, 7179 1°88 —o"09 
Group II. 
F cig: 71°52 71°67 —or15 
Near Brownsville, 71 - 7Uor Tr tee 
ee 72'1 7. +016 
Steubenville, * 72°56 72° +0°30 
N 72°53 72°24 +0°29 
y* 2°58 74-46 40:12 
vpn ae Part the dip has been found indirectly only, by means of be 
Lay nel seachall Wticincanteeisbs--2 in ousabecs. Total Minabor of 
