Variation and Dip of the Magnetic Needle. ~Al 
Art. V.—On the Variation and Dip of the Magnetic Needie in 
the United States; by Ex1tas Loomis, Professor of Mathemat- 
ics and Natural Philosophy in Western Reserve College. 
Communicated to the Conn, Acad. of Arts and Sciences, and read April 28, 1840. 
I. Variation of the Magnetic Needle. 
In the number of this Journal for July, 1838, (Vol. xxxiv,) I 
have given a collection of all the observations on the variation of 
the magnetic needle in the United States, which I had at that 
time been able to collect, and from them was enabled to draw up- 
ona chart the lines of equal variation with tolerable accuracy. 
The observations, however, exhibited various anomalies, and 
for the southern part of the country were very few in number. 
Further information on the subject was therefore desirable. I 
have accordingly sought observations from every source in my 
power; with what success the present article will show. 'The 
earliest information on the subject I have been able to obtain, is 
contained in the Journal of Hudson’s third voyage, in 1609, when 
he discovered Hudson River. The Journal is contained in the 
third volume of Purchas’s Pilgrims, from which the following ex- 
tract was furnished me by Prof. Jared Sparks, of Cambridge. 
Hudson came to the Grand Bank of Newfoundland, and proceeded 
along the coast to the thirty-fifth degree of latitude. He does 
not mention his ‘longitude, but was commonly in sight of land. 
July 3, 1609. Bank of Newfoundland. Lat. 44° varia. 17°w. 
ee et 15 
: s s Uncertain. “ 
& 5, tc Ps A103 
“10, “ Near Cape Sables. 2 ae Cm 
“« 25, “ Mouth of Penobscot River. 44 1 “ 10 
“¢ 626,. “ At Sunset. oles i 
“ 28, “ Farther S. towards Cape Cod. ee 
« 29, “  Sunset—near Cape Cod. Bd 
Aug. 11, “ Near the coast. ou ii = * ae 
* = tye. AS NOOR: 38 13 © 410 
¢ . 13" Atn0GR. 3624025". 78 
= 15, = ot 26 ee J 
te about 36 tira a 
Sept.13, “ A few miles up Hudson’s River, "> Ie 
6 
Oct. 4, “ At noon—on the coast. 39 30.) 
Vol. xxx1x, No. 1.—April-June, 1840. 6 
