AT LOUISVILLE, KENTUCKY, AND CINCINNATI, OHIO. 263 



Cincinnati, March, 3h. 30m., P. M., at my own house, in the garden. 



By needle No. 1, 70° 24'.25 



" No. 2, 70 22 .8125 



Mean, 70 23 .5312 



Mean dip at Cincinnati, 70° 25'. 5312* 



Louisville, March 10, 8/j. 13 jn., A. M. Jacob's Woods. 



By needle No. 1, 69° 55'.25 



" No. 2, . . 69 51 .375 



Mean, 69 53 .3125 



Louisville, March 11, 6/i. 23ot., A. M. Jacobs Woods. 



By needle No. 1, . . 69° 57' 



" No. 2, 69 56 .75 



Mean, . . . . ' . . 69 56 .875 



Louisville, March llth, 5h. 27m., P. M. 



By needle No. 1, 69° 55'. 125 



" No. 2, . , . 69 53 .75 



Mean, 69 54.4375 



Mean dip at Louisville, 69° 54'.8750. 



The relative total intensities at Louisville and Cincinnati, calculated from 

 the preceding elements of dip and horizontal intensity at the same places, are 

 as 1.0000: 1.0031. 



The following experiments were made to determine the correction for tem- 

 perature of these needles. 



A stove and pipe of copper were introduced into a room in my house, fifteen 

 feet square, and having no unusual quantity of iron about it. Opening the 

 room on the morning of the 22d of March, the apparatus was cooled down to 

 38° F., and the time of five hundred vibrations observed. It was then heated 

 as rapidly as possible by means of the copper stove to 91°.4, and the time of 

 five hundred vibrations again observed and noted. The constant coefficient 



* The dip determined at Longworth's garden since this period, namely, 21st of April, 1840, 



was, by Needle No. 1, 70o29'.68 



« No. 2, . . . . . . 70 28 



Mean, 70 28 .84 



