AT TWENTY-ONE STATIONS IN EUROPE. 



89 



by employing in the calculation the more accurate determination of the long 

 series just referred to. 



Professor Encke has determined from this series a formula by which the 

 dip may be calculated for any epoch, namely, 8 = 68° 7'. 3 — 3'.52 (t — 1836,) 

 in which S is the dip and t the year or fraction of a year. The dip in Decem- 

 ber, 1837, calculated from this formula, is 68° 00'.4, from which my result dif- 

 fers about eight minutes. 



MM. Humboldt and Gay Lussac determined, in 1809, the relative inten- 

 sities at Berlin and Paris to be 1.014; M. Erman, in 1828, and M. Quetelet 

 in 1829, 1.0165.* My determination is 1.0145. 



VIENNA. 



These observations were made in the Botanic Garden, upon the upper 

 platform. The chronometer was compared, before and after the observations, 

 with the observatory clock. The time of ten oscillations and the dip are com- 

 pared with the mean of the observations at Paris in 1837 and 1838, in calcu- 

 lating the horizontal and total intensities. 



Observations at Vienna. 





For Horizontal Intensity. 





Needle. 



Date. 



Temp. 



No. of 

 Series. 



No. of 

 Oscill'ns. 



Time of 



Ten 

 OsciU'ns. 



Coeffic't 



of 

 Corr'n 



for 



Loss of 



Magn'm. 



Horizontal 

 Intensity. 



Year. 



Month. 



D. 



H. 



Fah. " 



Sees. 



Paris 1.000. 



Cylinder. 

 Bar. 



1838 

 11 



March 



23 



4> 



31, P. M. 



41, " 



58.3 

 57.8 



2 



2 



700 

 700 



33.436 

 36.043 



1.0076 

 1.0023 



Mean, 



1.084 

 1.096 



1.090 



For Dip. 





1838, March 21, Needle No. 1, 64° 45'.8. 



No. 2, 53 .7. Mean, 64° 49'.7. 



Total Intensity compared with Paris as unity, 0.989. 





The only published observations of magnetic intensity at Vienna with which 

 I am acquainted are those quoted by Major Sabine, in his recent report, as 



* Major Sabine's Report on the Magnetic Intensity of the Earth. 



VII. — X 



