MAGNETIC SURVEY OF PENNSYLVANIA. 



(INCLUDING l'AKT OF OHIO AND MARYLAND.) 



FIRST MAGNETIC TOVll OF 1840. 



Abstract of Results for Relative Intensity and Dip at i(> Stations. 



Philadelphia. 



July 16 



Time. 



Needle. 



9 h 30 n 

 10 30 



Cylinder 

 Bar 



Temp. Fahr. 



76°.5 

 77.5 



No. of series. | No. of 

 \ ibrations. 



300 

 450 



T:n f 



10 vibrations. 



34 s . 51 

 36.85 



Corr'd. 



34".480 

 36.775 



I 



1.0000 

 1.0000 



Cumulus, wind N. W. 



July 21 



Needle. 



No. 1 

 No. 3 



Dip. 



71° 55'.8 

 71 50.1 



Temp. Fahr. 



70°.5 

 77.0 



Dip when loaded. 



— 1°09'9 

 + 1 09.1 



Dip reduced. 

 t 



71° 51'.4 

 57.4 



Mean 



71 54.4 



Lloyd Needle No. 1, weight in third hole of S. pole, or end B. 

 No. 3, Weight in last hole. 



(Old weights.) 



COS. 6 



Relative total intensity = — — y- r 



J sin. (S — 6) 



Relative total 

 intensity 



L.0453 



1.0586 



1.0520 



Reading, Pa.— (In middle of graveyard of TJniversalist Church.) Cloudy, wind B. of S. 



Dip. 



Temp. Fahr. ' Dipwhen loaded. 



8 



July 23 



No. 1 

 No. 3 



72° 29'. 7 

 72 31.9 



86°. 7 

 84.0 



—2° lit'. 4 

 + 36.6 



i>i[i reduced. 

 t 





72° 25'.3 

 72 39.2 



Relath 



intensity. 



1.0356 

 1.0512 



Mean 



72 32.2 1.043.4 



( 1 ) 



