96 



OBSERVATIONS OF THE MAGNETIC INTENSITY 



These observations having been made in August, 1837, are compared with 

 those at Paris in 1837, the dip being obtained, however, as in the similar case 

 of 1838, by using both series of observations. The rate of the chronometer de- 

 termined at Geneva v/as used in the reduction. 



Observations at Chamouni and the Flegiere. 



For Horizontal Intensity. 



Place. 



Needle. 



Date. 



Temp. 



M 



.2 

 <u 



o 

 d 



o 



Time of 



Ten 



Oscill'ns 



at 60°. 



Sees. 



Coeffic't 



of 

 Cbrr'n 



for 



Loss of 



Magn'm. 



Horizontal 

 Intensity. 



Year. 



Month. 



D. 



H. 



Fall. ° 



Paris 1. 



Chamouni 



Cylinder 

 Bar 



1837 



Aug. 



26 



9§,P.M. 

 10, " 



53.0 

 50.0 



1 



2 



150 

 300 



32.902 ! 1.002 

 36.006 1.001 



[ Mean, 



1.088 

 1.089 



1.0885 



The Flegiere 



Cylinder 

 Bar 



1837 



Aug. 



26 



12, M. 



121, P. M. 



68.0 

 69.5 



2 

 1 



650 

 300 



32.768 

 35.945 



1.002 

 1.001 



Mean, 



1.097 

 1.101 



1.099 



For Dip. 



Ch 



amouni, 1837, Aug. 26, Needle No. 1, 64° 38'.7 



No. 2, 64 37 .7 



Mean, 64° 38'.2. 







The Flegiere, 1837, Aug. 26, Needle No. 1, 6^ 



t° 35'. 8. 







Total Intensity at Chamouni, compared with Paris as 

 " " on tlie Flegiere, " " " 



unity, 0.979 

 "' 0.987 





The horizontal intensity in the Valley of Chamouni, according to Professor 

 Forbes, is 1.076,* and to M. Quetelet, 1.0935.t My result agrees nearly 

 with the latter. The higher station presents a greater horizontal and total in- 

 tensity than the lower, contrary to the general deduction from the laboured and 

 ingenious memoir of Professor Forbes on this subject. It is worthy of remark, 

 however, that the number given by Professor Forbes for the horizontal inten- 

 sity at the Jardin is greater than that for the valley. M. Quetelet, on the 

 contrary, found a less horizontal intensity on the Mer de Glace than at Cha- 

 mouni. The anomaly is probably real, and adds another to the instances pre- 

 sented by Professor Forbes, of the difficulties of the problem of which he has 



* Edinburgh Transactions, vol. xiv., part I. 



t Annuaire de rObservatoire de Bruxelles pour I'an 1834. 



