ABSTRACT AND REDUCTION OF OBSERVATIONS FOR DECLINATION. 



OBSERVED IN PENNSYLVANIA AND ADJACENT STATES IN 1S40 AND 1841. 



These observations were made with a Gambey Declinometer belonging to the 

 Girard College. 



One division (small) of the scale was found equal to 14". 54, as determined in 

 1844, at Sandy Hook, by Lieut. G. M. Bache (See Coast Survey records). 1 large 

 division = 60 small divisions. 



The observations were made with telescope direct, with slit to the right hand or 

 /•.'.. and with telescope inverted, with slit to the left or W.j also with needle direct or 

 hairs up, and with needle inverted or hairs down. With needle north, \Y. readings 

 are -4-, E. readings — ; with needle south, west readings arc — , cast readings +. 



Throughout the record the apparent direction (E. or W.) is given, the same is 

 to be understood in this reduction ; apparent E. is real W., and when the angle is 

 west of true north, apparent east is + f° r the north end of the needle, but as the 

 azimuth circle reads from north to east this sign is to be reversed if we apply the 

 correction directly to the circle reading. 



The accompanying papers contain also the reduction of the observations for time, 

 for azimuth, and for latitude. 



Declination Stations of 1840. 



1. Ilarrisburg. 4. Johnson's Tavern, near Brownsville. 



2. Huntingdon. 5. Irwin's Mill, near Mercersburg. 



3. Honiewood, near Pittsburg. 6. Baltimore. 



Chronometer, Grant No. 3861, London {Pocket Chr.). 



For chronometer error and rate. 



Chron. fast, Philadelphia time, July 21 . . . 5" 01 m 25*.0 



Pittsburg " Aug. 5 . 5 21 23.9 



Diff. long., 5 1 ' 20 m 08 s — 5" 00 m 40 s . 19 28 



Chron. fast, Philadelphia time, Aug. 5 

 Gain in 15 days 

 Daily rate = 2 B .0fi (travelling rate). 

 Between July 15 and July 21, the daily rate was 3".3 (stationary rate)- 



5 01 55.9 

 30.9 



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