88 



OBSERVATIONS OF THE MAGNETIC INTENSITY 



already stated. The coincidence of the two results shows strikingly the accu- 

 racy with which the curve already described supplies the data for the correc- 

 tion of the loss of force by the horizontal needles. 



The chronometer was compared with the observatory clock. 



Observations at Berlin. 



For Horizontal Intensity. 



Needle. 



Date. 



Temp. 



No. 



of 



Series. 



No. of 

 Oscill'ns. 



Time of 



Ten 

 Oscill'ns. 



Corrected 

 Time of 



Ten 

 OsciU'ns. 



Correction 



for 



Loss of 



Magnet'm, 



Horizontal 



Intensity. 



Year. 



Month. 



D. 



H. 



Fall. " 



Sees. 



Sees. 



Paris 1. 



Cylinder 



1837 



Dec. 



16 



2, P. M. 



37^ 



2 



690 



34.966 



35.006 



1837. 

 1.015 



1838. 

 0.975 



0.974 

 0.977 



Bar 



1 



1837 



K 



ti 



2| " 



35 



2 



660 



.37.886 



37.993 



1837. 

 1.005 



1838, 

 0.993 



0.983 

 0.984 



Mean, . . 



0.979 



For Dip. 



1837, Dec. 29, Needle No. 1, 68° 06'. 5 



No. 2, 68 10.6 Mean, 68° 08'. 5. 



Total Intensity compared with Paris as unity, 1.0145. 



The horizontal intensities of Berlin and Paris were compared by M. Rud- 

 BERG, who made the relation 0.974, and by M. Quetelet,* who gave 0.975 for 

 the relative intensities. My result differs but slightly from these. 



The dip at Berlin is very well known from a series of observations extend- 

 ing from 1806 to 1837, and my result can add nothing to the knowledge of this 

 element, but as obtained with the same instrument which was used at Paris, 

 the total intensity will be, probably, a nearer approximation by using it than 



* Annuaire de I'Observatoire de Bruxelles pour I'an 1834, p. 266. On the next page M. Quete- 

 let gives 0.9886 for the relative intensities, but this is doubtless a mistake. 



