94 



RECORD AND RESULTS OF 



The relation K= K^ ( /' \ gives ^^^Z^-— 0.19972 



We have therefore Ig (jvk) = 1.19402 for temperature 85° Fah., and taking the 

 coefficient of expansion of steel = 0.0000068 we find also Ig (jvlc) := 1.19378 for 

 temperature 45°. 



Determination of Magnetic Moment of Z 6 and of the Horizontal Force. 



Experiments of deflection. June 13, 1862. Magnet Z 6 deflecting at right angles to magnet Z 1 



suspended. Deflecting distance 1.35 feet.' 



Circle readings, 11'" 0". Temperature, 85°. 



Magnet. 



North end. 

 E. 



Order. 



1 



7° 



A. 

 3t' 00" 



B. 

 34' 40" 



Order. 















W. 











2 



1° 



3' 10" 



3' 



40" 





E. 



E. 



3 





32 30 



33 40 

















W. 











4 





3 00 



4 



00 







E. 



] 



5 



Mean, 





33 10 



34 10 



















33.7 







03.5 



2m = 0° 30 ,2 





W. 











6 





3 40 



4 



10 







E. 



1 





31 00 



38 00 















w. 



W. 

 E. 



9 





36 00 



36 40 



8 





3 40 



5 



00 







W. 



] 



Vtean, 









10 





3 40 



4 



40 









36.9 







04.1 



2m = 6 32.8 







it 



11 



I OC)m 



Temperatu 



re, 85^ 











M = 3 15, '7 5 



Line of detorsion, 177° 



For the determination of the coefficient P depending upon the distribution of the 

 free magnetism in the mamets, we have seven sets of observations of deflections at 

 distances of 1.0 (in one case of 0.9) and of 1.8 foot. By means of the distances r 

 and Vi and the corresponding angles of deflection i6 and u^ we have 



r r{ sm u-^ — r^ r sm u 



r{' sm Ui — r^ sm u 

 The observations themselves will be found in their proper place in this paper. 



Locality. 



Date. 



feet. 



u 



r, 

 feet. 



"i 



P 



Cambridge, 



1860. 



July 3 



1.0 



9° 



39' 02"- 



1.3 



4° 



24' 15" 



—0.0153 



Port Foullve, 



1861. 



July 2 



0.9 



49 



52 36 



L3 



14 



39 25 



+ 0.0044 



" 





7 



1.0 



34 



12 41 



1.8 



15 



13 51 



—0.0606 



" 





8 



1.0 



33 



58 36 



1.3 



15 



08 08 



—0.0607 



" 





9 



1.0 



34 



14 04 



1.3 



15 



24 53 



—0.0851 



Upernavik, 





August 16 



1.0 



26 



21 26 



1.3 



11 



37 53 



+ 0.0057 



Godhavn, 





September 7 



1.0 



19 



45 38 



1.3 



8 



59 49 



—0.0382 













IV 



"ean 







—0.0357 



This large value of P is occasioned by the fact that the two magnets are of 

 equal size. 



' Correction for defect of wooden Scale + 0.0003 foot. 



