and parts of adjacent States, . 365 
Recapitulation. 
No. Group. Latitude, Longitude. Date. Observed dip. _ 
10 i 39 57°1 76 16:8 1841-0 4 
7 IL 40 15°4 79 549 1840°6 72 13°2 
7 Kil. 41 48-0 79 57°4 1841 6 73 
10 IV. 4t 245 77 16°9 1841°4 IS 177 
6 43 12°1 77 38:6 18436 74 a 
8 VI 41 40-6 74 248 1842°9 73 47 
Mean, 41 23-1 77 349 1841 73178 
| (November) 
(Number of observations = 48.) 
_By comparing the differences in latitude and corresponding 
differences in dip, for each place, with the mean values of the 
ree their general accordance was ascertained. None of the 
&, Y, 2, p, g, a8 well as 2, are to be determin ication 
of the method of least squares, from the observations 
themselves. 
Locality. Date. | Dip. | Date. Dip. ee Annual 
° 4 | ne 
| Washington, ca 1841 7 15° Aug. 1862 | 71 190 +015 
Harrisburg, July 1840 | 72 20 July“ 72 316 +0 50 
Near Brownsville, Aug. “ at 535 atta 71 56°9 +015 
« 1841 | 73 466 Aug.“ 73 52:2 40°27 
a sia): :|fe | se 
liamsport, a ~ 72 544 . . 72 51-0 -~o'f 
Philadelphia,’ Feb. 1842 | 71 571 Ae 72 058 +0°4 
; oe Mean, |i) +0718 
Am. Jour. Sc1.—Srconp Series, Vou. XXXV, No. 105.—May, 1863, 
47 
