ASTRONOMICAL OBSERVATIONS. 



39 



by a mofi: excellent tranfit inftrument, made by Mr. Bird, and 

 which had been ufed by Meffrs Mafon and Dixon, fome years 

 before in this country. 



The magnetic variation was taken in many places on this line, 

 and was found at our firfl ftation at the end of the parallel of 



>Eaft. 



The ftate of Pennfylvania is bounded on the north by the 

 42° of north latitude. This line extends from a point on the 

 Delaware, (which was fixed by Dr. Rittenhoufe and Captain 

 Holland in the year 1774,) and extends wefl to Lake Erie: 

 it was completed in the years 1786, and 1787. In order to 

 carry on the parallel of latitude with as much expedition, and 

 economy as poffible, we difpenfed with the method of tracing 

 a line on the arc of a great circle, and correcting into the paral- 

 lel, as purfued by Meffrs Mafon and Dixon, in determining 

 the boundary between this flate, and the ftate of Maryland, 

 and which we followed in completing their line in the year 1784. 

 We commenced our operations by running a guide line weft, 

 with a furveying compafs from the point mentioned on the 

 F 2 , Delaware 



