AT TWENTY-ONE STATIONS IN EUROPE. 



87 



Observations for Horizontal Intensity at Brussels. 



Needle. 



Dat^. 



Temp. 



Number 



of 

 Oscill'ns. 



Time of 



Ten 

 Oscill'ns. 



Corrected 

 Time of 



Ten 

 Oscill'ns. 



Mean. 



Correction 



for 



Loss of 



Magnetism. 



Hor. 

 Intensity. 



Tear. 



Month. 



D. 



H. 



Fall. ° 



Sees. 



Sees. 



Sees. 



Paris 1. 



Cylinder. 



(( 



Bar. 



1838 



n 

 hi 



July 



25 



a 



2i, P.M. 



2i, " 

 3^, " 

 51, " 



62 

 61 

 60 

 57 



300 

 300 

 350 

 350 



35.596 

 .599 



38.366 

 .334 



35.640 

 .644 



38.417 

 ,398 



35.642 

 38.407 



1.0026 

 1.0002 



0.968 

 0.970 



The mean of these results, 0.969*, is in close accordance with the results 

 before referred to as given by M. Quetelet, the mean of the several series of 

 observations made at Brussels between 1828 and 1838 being nearly 0.964. , 



BERLIN. 



I am indebted for an opportunity to make this set of observations to the 

 kindness of Professor Encke, who. put his convenient magnetic observatory 

 at my disposal, and removed from it the variation magnetometer and dipping 

 needle which it contained : without this, I could not have observed at this sea- 

 son of the year. In my first attempts to obtain the dip I was unsuccessful, 

 owing to the great loss of force which my magnets for reversing the poles of 

 the dipping needle had sustained during a circuitous journey from Switzerland 

 to this capital. The magnets were retrenched by (Ertel, and the results then 

 obtained appear worthy of confidence. Since this time I have taken the pre- 

 caution to oscillate the dipping needles before observing with them after the 

 reversion of the poles, to ascertain that they are charged nearly, or quite, to 

 saturation. As the periods which elapsed between these observations and 

 those which preceded and succeeded them, at Paris, were not very different, I 

 have calculated the intensity at Berlin in reference to both the series at Paris, 

 applying the correction for the loss of magnetism by the needles, deduced as 



* This number differs by 0.001 from the result given by M. Quetelet in the Bulletin of the Brus- 

 sels Academy, vol. v. p. 481. In the numbers communicated to him I had applied a correction for 

 the loss of magnetism of the needles which was too high by nearly this difference; which is, how- 

 ever, entirely unimportant. 



