262 HORIZONTAL MAGNETIC INTENSITY AND DIP 



By comparing these double suites of experiments made at each of the places, 

 Cincinnati and Louisville, I obtain the following ratios of horizontal intensity : 



Cincinnati, March 1th, and Louisville, March lOth, 1840. 



Lou. Cin. 



By needle No. 1, ......... 1: 0.9733 



" No. 2, 1: 0.9723 



" No. 3, * . . . . 1: 0.9730 



Cincinnati, March 1th, and Louisville, March l\th. 



By needle No. 1, . . . 1: 0.9755 



" No. 2, 1: 0.9735 



" No. 3 1: 0.9734 



Cincinnati, March 14fA, and Louisville, March 10th. 



By needle No. 1 I 



" No. 2, 1 



'.' No. 3, 1 



0.9720 

 0.9698 

 0.9723 



Cincinnati, March lith, and Louisville, March 11 th. 



By needle No. 1, '. . - . 1: 0.9742 



" No. 2, . . . 1: 0.9709 



" No. 3, 1: 0.9726 



Mean, 1: 0.9727 



We have, then, the horizontal intensity at Louisville to that at Cincinnati 

 as 1 to 0.9727. 



Magnetic Dip. 



Cincinnati, March 6th, 1840, 2/;. 30m., P.M. Longworth's Garden. 



By needle No. 1, 70° 27'.25 



" No. 2, 70 27 .8125 



Mean, . , . . , 70 27 .5312 



