292 



OBSERVATIONS OF THE 



The same conclusion might be derived from these observations as from those 

 at Detroit, with regard to the inutility of multiplying beyond a certain point 

 the observations at one place. If the observations are to be repeated, the object 

 being to obtain the mean dip of the place, it seems better to change the locality, 

 if it be only by a few rods, by which means any disturbing causes of limited 

 extent will probably be detected. 



Magnetic Dip at Fort Brady, Michigan. Latitude 46° 30' N.; Longitude 84° 24' W. 

 Place of observation fifty rods south-east of the south-east angle of the fort. 



Date. 



Hour. 





Needle. 



No. 



Readings. 



i 



Dip. 



1841, Aug. 25, 



2—5, P. 



M. 



No. 1, 





40 



77° 



25.3 



(( 







No. 1, poles reversed, 





40 





33.1 



(C 







Mean of No. 1, 





80 





29,2 



it 







No. 2, 





40 





28.5 



(( 







No. 2, poles reversed, 





40 





25,4 



(( 







Mean of No. 2, 





80 





27.0 



<( 







Mean of both needles. 





160 



77 



28.1 



Observations repeated eighteen Rods South-West of th 



e last Station. 







Date. 



Hour. 





Needle. 



No. 



. Readings. 





Dip. 



1841, Aug. 25, 



5—7, P. 



M. 



No. 1, 





40 



77' 



' 33',0 



i( 



(1 





No. 1, poles reversed, 





40 





25.4 



<( 



« 





Mean of No. 1, 





80 





29.2 



(( 



(( 





No. 2, 





40 





25.5 



« 



(( 





No. 2, poles reversed. 





40 





27.2 



« 



(( 





Mean of No. 2, 





80 





26.4 



(I 



t< 





Mean of both needles. 





160 



77 



27.8 



( 



Observations repeated near 



' the River, at the foot of 



the 



Rapids. 







Date. 



Hour. 





Needle. 



No 



. Readings. 





Dip. 



1841, Aug. 27, 



5—7, A. 



M. 



No. 1, 





40 



77' 



° 36.9 



t( 



(( 





No. 1, poles reversed, 





40 





30.3 



(( 



a 





Mean of No. 1, 





80 





33.6 



(( 



i( 





No, 2, 





40 





29.5 



(( 



(( 





No. 2, poles reversed, 





40 





36.2 



K 



<( 





Mean of No. 2, 





80 





32,9 



(( 



(( 





Mean of both needles. 





160 



77 



33.2 



Mean of 480 i 



eadings with both needles, 



• • « • 



. 



. 



Ti 



' 29,7 



