THE VARIATION OF THE NEEDLE AND THE LOCATION 

 OE THE ISOGONIC LINES IN NORTHERN NEW YORK. 



[Read before the Albany Institute, February 3, 1885.] 



The first paper in the first volume of the transactions of the Albany 

 Institute is entitled a "Table uf variations of the magnetic needle, 

 from data in the possession of Gen. Schuyler; " and was prefaced by 

 some brief, but interesting remarks by the Hon. Simeon De Witt, 

 then Surveyor-General of New York. This paper was presented on 

 the 27th day of April, 1825, probably a short time after the actual 

 consolidation of the parent associations — the Society for the Promo- 

 tion of the Useful Arts, and the Lyceum of Natural History — that 

 carry the history of the Albany Institute back into the previous cen- 



In this paper the Surveyor-General refers to his settling in Albany, 

 in 1785, at which time, he says, "I established a true meridian, on 

 which I occasionally set a compass for the purpose of observing the 

 variation of the needle; and from these observations I found no 

 reason for departing from the old rule until 1807; when, to my sur- 

 prise, I found that a sudden change had taken place in the direction 

 of the needle." 



Mr. De Witt then proceeds to tell of his discovery of the change 

 of direction of the annual movement of the magnetic needle, from an 

 easterly to a westerly variation at Albany in the year 1807, and states 

 that at the time of the writing of his paper, his observations showed 

 that the amount of what he terms the "retrograde" motion of the 

 needle, was found to be two minutes of arc per year. To make the 

 meaning more pln-in, we may say that the" retrograde" movement, as 

 he calls it, was a gradual movement of the north point of the needle 

 to the westward, a change in the annual resultant of magnetic force, 

 which had previously been tending eastward. 



It is an interesting fact that the first practical steps toward the 

 application of even proximate scientific principles in the use of the 

 magnetic needle on the land surveys of our State originated in the 

 halls of the Albany Institute, and was the work of a State officer who 



