42 Variation and Dip of the Magnetic Needle. 
On the 2d of September, when he was near the Jersey shore, 
a little below the mouth of Hudson’s River, he says: ‘This 
night I found the land to haul the compass eight degrees. For 
to the northward of us we saw high hills. For the day before we 
found not above two degrees variation.’ 
Most of the preceding observations were of course made on ship- 
board, and perhaps all, with the exception of that of Sept. 13th. 
The iron of the vessel would necessarily influence the needle to 
an amount which we have, perhaps, no means of estimating. 
The observation of Sept. 13th, it is presumed, was made on shore, 
and may be compared with subsequent observations at New York 
city. The variation here in 1686, according to Mr. Welles, was 
8° 45’, showing a decrease of 4° 15’ in seventy-seven years, or 
about three and a third minutes per year. This accords very 
well with subsequent observations at the same place. 
Most of the other observations which I have obtained are of 
recent date. ‘The Geological Reports of Maine, New York, Geor- 
gia, Ohio, and Michigan, have furnished the principal part. In 
September, 1839, I obtained a few observations from the Gene- 
ral Land Office at Washington; a few are from the New York 
Regents’ Reports, and the remainder are from miscellaneous 
sources. ‘The catalogue is here subjoined; the stations being 
arranged by States, commencing with the most easterly, 
Observations on the Variation of the Magnetic Needle in differ- 
ent parts of the United States. 
| Place. | Lat. N. (Lon. W.) Variation. | Date. Authority. 
MAINE. e Sie cis | 
N. E. angle of State, [48 067 37/19 12 w/I838/State Comm’rs. 
Greenville, 45 2469 35/11 0 | “ {Third Geo. Report. 
Farmington, 44 42:70 4/11 20 é a 
Umbagog Lake, 44 42'70 53/13 0 | « - 
Dixfield, 44 32'70 14/12 0 “6 a 
Rumford, 44 30:70 26/11 0 ss = 
Waterville, 44 2869. 32112 8 |1835) = 
Belfast, 44 2668 54/13 0 |1838 se 
Raymond, 43 57/70 24| 9 45 * 
West Thomaston, 43 5669 512 0 - be: 
NEW HAMPSHIRE. 
Hanover, 43 42'72 10| 9 15 = |1839|Prof. Young. 
VERMONT. ; 
{Burlington, 44 2773 10| 7 36 |1826|Prof. G. W. Benedict. 
_ MASSACHUSETTS. 
Willia: >. (42 43173 13] 6 15 hs Prof. A. Hopkins. 
“ We ete 7 45 1837] “ss 6“ 
