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. 



Castle of Heidelberg, 1.020 \ 



Town of do. . 1.024/ 



Konigstuhl (summit), . . ... . . 1.027 



Geneva, 1.080 



Chamouni, ........ 1.093 



St Bernard, 1.097 



Martigny, . : . ... . . 1.092 



Forbes, No. I. 



1.017 



1.018 

 1.076 

 1.085 

 1.082 

 1.083 



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

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

 observations relatively to Geneva as a fundamental station, taking the data firom 

 Table VII. and writing the equations of condition in the form (8) art. 28, where 

 «! 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 aU this), we shall have 

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

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

 lated. 



Table VIII. 

 Equations of Condition for the Alpine Series. 





















By No. I. 



By " Flat 



Geneva (Aug. 1832), . 



O'x 



+ 



O'y 



+ 



Oz 



+ 



H' 



= 



.002 



.005 



Geneva (Nov. 1832), . 



Ox 



+ 



Oy 



+ 



Oz 



+ 



H' 



^ 



— .002 



— .005 



Mont Saleve, 



— 6a? 



+ 



2.V 



+ 



82 z 



+ 



JF 



— 



.001 



.002 



Mont Breven, 



. — 16 a? 



+ 



4:1 y 



+ 



71 z 



+ 



H' 



= 



.013 



.024 



Chamouni, 



. —Vjx 



+ 



A3y 



+ 



21 z 



+ 



sr 



= 



.009 



.005 



5. 



* 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 V Academic dc Bruxclles, tome iv. ; and an abstract in the 

 Annuaire dc V Observatoire de Bruxclles, 1834. 



c2 



