64 



OBSERVATIONS TO DETERMINE THE MAGNETIC INTENSITY 



between 1839 and 1840. This is believed to be due to rust contracted in the 

 interval. As, however, the rust was contracted after the subsequent obser- 

 vations, the magnetism of the needle throughout the series is regarded as 

 invariable. The stations of observation were the same as for the dip formerly 

 described, with the exception of that at Dorchester, which was near Mr. Bond's 

 Observatory. 



Place. 



Date. 



Needle. 



rime of 280 | 

 Vibrations. Temp. 



Corrected 

 Time. 



New Haven, Conn. 



1839 



, Sept. 11, 



9^ 53'° 



A.M. 



Sabine 



760^64 



81°.8 



755^21 



(( 



(( 



(( 



10 24 



a 



n 



763 .34 



83 .0 



757 .59 



(( 



(( 



<i 



10 55 



11 



Hansteen 



887 .04 



76 .4 



884 .27 



(( 



a 



(( 



11 24 



a 



Henry- 



609 .95 



74 .8 



608 .90 



Dorchester, Ms. 



(( 



Sept. 18, 



4 48 



P.M. 



Sabine 



778.24 



78 .8 



773 .45 



i( 



if 



(( 



5 34 



a 



Hansteen 



907 .06 



75 .7 



904.35 



a 



(( 



(( 



6 



a 



Henry- 



625 .08 



72 .6 



624 .17 



Providence, R. I. 



a 



Sept. 19, 



4 59 



(( 



Sabine 



769 .32 



70 .4 



766.70 



(( 



«( 



H 



5 22 



(C 



Hansteen 



898 .92 



68 .5 



897 .46 



Princeton, N. J. 



(( 



Sept. 21, 



4 51 



n 



Sabine 



739 .24 



80.7 



734 .22 



it 



(( 



(( 



5 40 



(( 



Hansteen 



865 .46 



79 .2 



862 .29 



a 



<( 



<< 



6 3 



(i 



Henry- 



595.10 



76 .9 



593 .93 



Philadelphia, Penn. 



(( 



Sept. 23, 



4 46 



(( 



Sabine 



729 .26 



70 .3 



726 .80 



(C 



(( 



(< 



5 23 



(( 



Hansteen 



851 .68 



67.6 



850.45 



(( 



(( 



(( 



5 47 



(( 



Henry- 



585 .28 



65 .7 



584 .89 



Hudson, Ohio. 



(( 



Nov. 2, 



1 23 



(< 



Sabine 



733 .85 



58 .1 



734 .31 



n 



<( 



(« 



1 41 



(( 



(t 



734 .75 



55 .1 



735 .93 



(C 



(( 



(( 



2 7 



ii 



Hansteen 



858.13 



54 .1 



859 .09 



(( 



(( 



(( 



2 27 



<f 



(( 



857 .66 



51 .6 



859 .03 



(( 



(( 



(C 



2 52 



(( 



Henry 



592 .61 



52 .1 



593 .15 



(( 



<( 



(( 



3 5 



(( 



a 



591 .41 



53 .0 



591 .89 



(t 



n 



Nov. 30, 



1 46 



It 



Sabine 



732 .70 



47 .6 



735 .68 



(( 



t( 



(( 



2 3 



il 



a 



732 .76 



42 .6 



736 .94 



<( 



li 



(< 



2 24 



(( 



Hansteen 



858 .59 



41 .0 



861 .70 



<c 



li 



C( 



2 45 



(< 



(( 



858 .33 



39 .8 



861 .63 



<( 



(( 



(( 



3 10 



(( 



Henry- 



591 .78 



39 .1 



593.21 



(( 



(( 



ii 



3 23 



(( 



(( 



591 .54 



38 .2 



593 .04 



«( 



184C 



, Jaa. 1, 



1 40 



<( 



Sabine 



731 .48 



23 .5 



740 .23 



C( 



a 



(( 



1 55 



(( 



a 



730 .36 



21 .5 



739 .57 



. (( 



a 



a 



2 29 



<( 



Hansteen 



856.63 



25 .5 



862 .26 



(( 



n 



<( 



3 41 



(( 



Henry- 



590 .75 



27 .0 



593.01 



<c 



(< 



(I 



3 55 



(( 



t( 



592 .47 



16.9 



595 .44 



The mean of the preceding observations furnish us with the following table, 



in which column third is computed from the formula — = f T=i ) j and column 



sixth by multiplying the horizontal intensity by the secant of the dip. The 

 last column represents the total intensity, that of New York being called 1.803, 

 according to the determination of Major Sabine. 



