OBSERVATIONS ON THE MAGNETIC DIP AND DECLINATION. 359 
Dip, by one hundred and forty-four observations on needle No. 1, made 
June the 29thiand 80th; 484i secant? is oSers Dao iSO. 60. 7H? 16788 
Dip, by one hundred and forty-four observations on aide No. 2, made 
June 30th, 1841, .. .. ..°. NS sue SOA 7'.72 
Magnetic dip, by a mean of two punndied dnd viginipa noigjed sabanigcin, in- 
ChidiO® both meedios,. ) .. uaF AS gl ee amet aes 
Nors.—A mean between the greatest and least dip obtained, being by two different needles, is '74° 18'.44. 
A mean between both needles in the night, say from 8h, 18m., P.m., to 3h. 34m., a.m., the middle time being 
within seven minutes of midnight, is 74° 16’.11. 
A mean between both needles in the day, say from 10h, 22m., a.m., to 1h, 55m., p.m., the middle time being 
eight minutes after noon, is 74° 19.65. 
A mean between the midnight and the mid-day results, as above, is '74° 1'7’.88. 
XX. Boston, July 2d, 1841. 
On the common or mall. ‘The position of observation is two hundred and fifty feet 
east by south of the summit of the old redoubt, or battery hill, the instrument being 
under the shade of asmallelm tree. Latitude 42°21'19”, N.; Longitude 71° 04’ 12”, W. 
NEEDLE No. 1. 
Marked’end. Rosie. Gheartetied. ‘Temperature. Dip observed, 
N 24. 7h. 13m., A.M. 68° 74° 03'.49 
Ss 24. 8 25 . 70 74° 13'.33 
Dip, by forty-eight observations on needle No.1, . . . . . . 74° 08.41 
NeeEpie No. 2. 
Ss 24 9h. 29m., A.M. ° 70°.5 74° 08'.33 
N 24. 10 53 “ 74. 74° 12'.58 
Dip, by forty-eight observations on needle No.2, . . . . 74° T0'.45 
Dip, by a mean of ninety-six observations on needles Nos. 1 aac Mn ee oe 
XXI. Bangor, Maine, July 9th, 1841. 
In the vacant lot of Mr. A. M. Roberts. Latitude 44° 48’, N.; Longitude 68° 47’, W. 
NEEDLE No. 1. 
Ss 24. Ih. 35m., P.M. 75°.5 76° 17.41 
N 24. 2 38 i 75 76° 09'.14 
Dip, by forty-eight observations on needle No.1, . . . . « . 76° 13'.27 
NEEDLE No. 2. 
N 24. 6h. 10m., P.M. 67°.5 76° 11.89 
S 24. OTOL a 65 76° 09'.71 
Dip, by forty-eight observations on needle No.2, . . . . . . 76°10'8 
NeeEpiLE No. 1, REPEATED. 
N 16 7h. 51m., P.M. 62°.5 76° 09'.27 
Ss 8 8 26 i 62 76° 13'.87 
Dip, by twenty-four observations on needle No. 1, second trial, . 76° 11’.57 
The late hour of the evening prevented more than eight readings on needle No, 1, 
with the polarity south, second set. 
VOL. 1X.—-94. 
