MAGNETIC OBSERVATIONS. 
81 
OBSERVATIONS—Continued. 
Station, Cambridge Observatory ; latitude 42° 22' 48"; longitude ih. 44 m, 29. 6s. 
Needle, B. Date, August 9, 1850. Hour of beginning, Oh. 40m. p. m.; hour of ending, C h. 50m. p.m. 
Observers, Trof. IF”. C. Bond and Lieut. A. TF. Whipple. 
o ' " 
l 47 00 
Needle vertical, face of circle north, reading of azimuth circle----] 47 29 
( 47 07 
1 48 26 
Needle vertical, face of circle south, reading of azimuth circle__-_4 48 15 
( 48 40 
Reading of azimuth circle when plane of instrument is in the magnetic meridian..__ 47 49 30 
Reading of azimuth circle when plane of instrument is in the true meridian_ 38 18 45 
Approximate magnetic declination___ 9 30 45 W. 
OBSERVATIONS FOR MAGNETIC INCLINATION AND INTENSITY—No. 4. 
Face of circle. 
Direct. 
Def. with wt. 1J gr. 
Def. with wt. 2% gr. 
Def. toward 
the vertical. 
(1) 
Def. from 
the vertical. 
(2) 
Ther. 
Fah. 
Def. toward 
the vertical. 
(1) 
Def. from 
the vertical. 
(2) 
Ther. 
Fah. 
East_| 
O ' 
74 30 
74 28 
74 25 
74 22 
74 30 
74 20 
O ' 
79 55 
80 05 
80 07 
O ' 
C8 55 
68 45 
68 45 
o 
75 
O ' 
104 00 
104 05 
104 05 
O ' 
44 35 
44 17 
44 15 
o 
75 
West___| 
Means_ 
o ' " 
74 25 50 1 
O ' " 
(1) 80 01 10 i 
(2) 68 24 10 \ 
75 
O ' " 
j (1) 104 01 40 ) 
j (2) 44 11 10 f 
Differences___ 
o ' " 
11 37 00 
o ' " 
59 50 30 
Half differences, or angles of de¬ 
flection ____ 
O ' " 
5 48 30 
O ' " 
29 55 15 
Sum of means... 
O ' " 
148 25 20 
O ' " 
148 12 50 
Half sum — dip_ 
o / // 
74 12 40 
o / " 
74 6 25 
11 m 
