GEOGEAPHICAL POSITIONS. 75 



Bideration of a jyrimnry meridian for the western world one necessary to be detennined 

 in the early state of the operations. 



The Capitol of Washington would naturally appear to be the fittest starting point ; but 

 as the introduction of greater diversity in astronomic and other Tables than at present 

 exists is certainly not desirable, the United States Survey' Department commissioned 

 Professor Bache to report on the subject. Impressed with the inconvenience attached 

 to the introduction of a fresh mode of reckoning meridional distances, and at the same 

 time to give due importance to the geodetical operations carried on in America quite 

 independent of any in the eastern hemisphere, he recommended, if any transatlantic 

 meridian were to be assumed as a primary, that of New Orleans would be the fittest. 



The progress of the survey having shown that New Orleans was in long. 90" 0' 0", or 

 nearly so, it became manifest that one objection to a new fractional element being intro- 

 duced was in some degree removed if this were taken. "With this view, if any meridian 

 were to be assumed for the United States, that of 90° West of Greenwich, ichej-ever it 

 may fall, is the fittest. If in the course of the operations any correction be found 

 necessary to this meridian, as marked in some part of New Orleans, let it be removed 

 accordingly. Thus the first meridian of the United States would be one-fourth of the 

 circumference of the globe, or six hours in time. West of that of Greenwich. 



VARIATION OF THE COMPASS. 



The question of Magnetic Variation or Declination received much attention from the 

 United States Survey Department, under the superintendence of Professor Bache, who. 

 with Mr. J. E. Hilgard and other ofiicers, have reported on the subject. The amounts 

 given in the Table can only be considered as approximate. 



The line of No Variation intersects the coast about Charleston. To the north-eastward 

 of this line, the Westerly variation is increasing about 3^' per annum in the vicinity of 

 Cape Hatteras ; about 3;^' per annimi near New York, and on the Coast of Maine. 



The lines of equal variation run about N.W. and S.E. true on the Coast of Maine ; 

 N.W. by N. and S.E. by S. about New York; and N.N.W. and S.S.E on the Coasts of 

 Carolina and Georgia. 



