loa 



Rev. Mr Scoresby on the Uniform Permeability of' 



As the results in the 6th column appeared to differ too con- 

 siderably to be at all satisfactory, the last three columns were 

 added in order to determine the real nature and extent of the 

 apparent discrepancies. Taking the mean of the ratios at 

 74)000, in round numbers (which was found to be sufficiently 

 near the truth), and applying that in a contrary way to the 

 magnetic forces belonging to the different distances, the column 

 of" calculated tangents^** was obtained, the resulting angles of 

 which, with only one or two exceptions, correspond with those 

 obtained by experiment within the probable limits of error of 

 observation *. 



• The compass employed being only graduated to 30' of a degree, and 

 without any vernier, it required some habit and attention to observe the an- 

 gles within such small limits as those indicated by the column of differences. 



