ARTICLE V. 



Observations to determine the Magnetic Intensity at several Places in the United 

 States, with some additional Observations of the Magnetic Dip. By Elias 

 Loomis, Professor of Mathematics and Natural Philosophy in Western Re- 

 serve College. Read Nov. 6, 1840. 



Magnetic Intensity. 



In the autumn of 1839, while engaged upon a series of observations for the 

 magnetic dip, the results of which are given in the Society's Transactions, Vol. 

 VII, pp. 101 — 111, Professor Renwick of New York kindly offered me the use of 

 his apparatus for magnetic intensity. The offer was gladly accepted, and 

 observations made with the needles whenever circumstances would permit. 

 As I had not yet learned to observe alone, and it was seldom I could find a 

 suitable assistant, the observations were few in number; and I should not 

 think them worthy the attention of the Society, were it not that they furnish 

 an approximate value of the magnetic intensity at one station somewhat re- 

 mote from the Atlantic coast, and in a region where such observations have 

 been seldom attempted. 



The apparatus employed in these observations was constructed after the mo- 

 del of that of Professor Hansteen. Three needles were used. The first, made un- 

 der the direction of Professor Hansteen himself, is 2.35 inches in length, and 

 .16 inch in diameter, mounted in a stirrup of parchment. The second, which 

 was furnished by Major Sabine, is 2.34 inches long, and .14 inch in diameter, 

 mounted in a brass stirrup. The third, by Professor Henry, is 2.40 inches 

 long, .15 inch in diameter, mounted in a silk stirrup. The needles are accor- 



VIII. — Q 



