46 



MAGNETICAL OBSERVATIONS. 



The value of log. n'K was computed for the following temperatures :— 

 At temp. 76° log. ^^K= 1.41047. 

 " 50 log. rt=A'= 1.41032. 

 Change of log. Tt'Khr 1° F., 0.6 units of the 5th decimal. 



The observations of deflection at distances of 1 foot and 1.3 feet, and at five different stations, give the 

 value of the induction-coefficient P: — 



Station I. 1856, August 7 . . . 7^= + 0.0004 



" II. 1856, August 17 

 " V. 1856, October 10 

 " VI. 1856, December 10 

 " VIII. 1857, January 26 

 Mean 



— 0.0007 



— 0.0085 



— 0.0037 

 + 0.0118 



P= — 0.0001 



This value of P is so small that it was neglected in the computation of the intensity. 

 The experiments of vibrations and deflections at the same five stations give for the magnetic moment 

 m of magnet D 3. 



Station I. 1856, August 7 

 II. 1856, August 17 

 V. 1856, October 9 

 " VI. 1856, December 10 

 " VIII. 1857, January 25 



The means of the 1st and 2d, and of the 3d and 4th values give : — 



1856, August 12 . . . m = 0.494S, temperature 80° 



1856, November 9 . . . m = 0.4907, " 72 



Loss of magnetism for ten days 0.00046.' 



From these the values of m were interpolated for the two stations, at which no experiments of deflec- 

 tions have been made, viz :— 



Station III. August 26 

 " IV. September 17 



m and X are expressed in feet and grains. 



TO = 4942 

 0.4931 



' Mr. Chas. A. Schott found 1855, September 13, (« = 0.5104, which gives the loss in 334 days = 0.0156, or the 

 loss in 10 days 0.00047, sliowing a very regular decrease of the magnetism of D 3. 



