TERRESTRIAL MAGNETIC INTENSITY. 19 



zontal intensity, that at Paris being = 1 ; both needles giving the same mean re- 

 sult to fom- decimal places. Professor Hansteen has given .8428, which must be 

 considered as a close coincidence.* 



For Brussels I find by "No. 1," 0.960 



by " Flat," 0.965 



Captain Sabine • 0.951 



M. QuETELET (4 series), 0.964 



M. RUDBERG, 0.971 



I subjoin a few comparisons of stations common to M. Quetelet's seriesf and 

 mine. 



Quetelet. Forbes, No. I. 



Castle of Heidelberg, 1.020| j qj^ 



Town of do. . 1-024 J 



Konigstuhl (summit), . . ... • • 1-027 1-018 



Geneva, 1-080 1-076 



Chamouni, 1-093 1.085 



St Bernard, 1-097 1-082 



Martlgny, 1.092 1.083 



30. But to return to the calculation of the first group of observations, those 

 includmg the alpine country of Switzerland, Savoy, and Italy. If we arrange the 

 obsei-vations relatively to Geneva as a fundamental station, taking the data from 

 Table VII. and writmg the equations of condition in the form (3) art. 28, where 

 a, denotes the excess of northern latitude of the given station above that of Ge- 

 neva in minutes ; h^ the excess of eastern longitude in minutes of a degree ; Cj 

 the excess in height, reckoned in hundreds of English feet in round numbers 

 (using of course negative signs to represent the reverse of all this), we shall have 

 the following equations of condition, distinguishmg from one another the absolute 

 numbers obtained by the two needles, in order that they may be separately calcu- 

 lated. 



Table VEI. 

 Equations of Condition for the Alpine Series. 



Geneva (Aug. 1832), 

 Geneva (Nov. 1832), 

 Mont Saleve, 

 Mont Breven, 

 5. Chamouni, 



* Since this paper was read, this result has been still more nearly confirmed by the observations 

 of Professor Bache of Philadelphia, who, by connecting Edinburgh and Dublin, and taking Professor 

 Lloyd and Captain Sabine's observations for the comparative intensities at Dublin and Paris, has ob- 

 tained the number .8400. 



t See his two papers in the Memoires de I' Academie de Bruxelles, tome iv. ; and an abstract in the 

 Annuaire de V Observatoire de Bruxelles, 1834. 



c2 



