THE MAGNETIC DECLINATION IN PRINCE 

 GEORGE'S COUNTY 



By 

 L. A. BAUER. 



TXTEODLTCTOKY. 



Values of the magnetic declination of the' needle, or of the "varia- 

 tion of the compass/' as ohserved hy the Maryland Geological Survey, 

 the United States Coast and Geodetic Survey, and the Carnegie 

 Institution of Washington at various points within the county are 

 given in the following table : 



For a a:eneral description of the methods and instruments used, 

 reference must he nuule to the ''First Eejxn-t upon .Magnetic Work 

 in Maryland" (Md. Geol. Survey, vol. i, pt. v, 1897). In the 

 Second Report (Md. Geol. Survey, vol. v, pt. i, 1005), the various 

 values collected were reduced to January 1, 1900: they are now 

 given also for January 1, 1905 and 1910, and some additional values 

 have been added. The First Report contains an historical account 

 of the phenomena of the compass needle and discusses fully the 

 difficulties encountered by the surveyor on account of the many 

 fluctuations to which the compass needle is subject. To these Reports 

 the reader is referred tor any ad<litioual details. 



Meridiaa^ Lixk. 



At the request of the State Geologist, the Superinten(h'nt of the 

 Coast and Geodetic Survey detailed 'Mv. J. B. Baylor in 1900 to 

 establish a surveyor's meridian line at the county seat. Upper ^Marh 

 boro. As the grounds around the court-house were not suitable fof 

 the purpose, the line was placed on the grounds of tlie Academy. 

 The line was marked l)y two st<uie posts, each bearing a brass cap 

 lettered U. S. C. cV G. S. ; the south stone is 75 feet from the front 



