258 TERRESTRIAL MAGNETISM AT HALIFAX. — DIXON. 



A small electric hand lamp was used for reading and for 

 illuminating the cross hairs when determining azimuth. 



Results. 

 The Declination was found to be 21° 2', local time 1 h. 40 m. 

 a. m., Aug. 26, temp. 15° C. 



This value has not been corrected for daily variation, the 

 amount being undetermined for Halifax. This correction would 

 be very small, as for all stations south of the 49th parallel it is 

 found that the yearly average diurnal variation is at a mini- 

 mum at about 2 a. m., being O'O at Madison, Wis., and 0'"5 at 

 Toronto. 



The value of the Dip found was 73' 58'; this was the mean 

 of two sets of observations, 74° 00' and 73° 55'. 



The Horizontal Force was found to be -1624, Aug. 25, 1904, 

 local time 3 a. m., mean temp. 13°'8 C. 



The Azimuth was determined by observations on Polaris, 

 these reductions being made by the tables published in the 

 U. S. " Manual of Instructions " issued by the Commissioner of 

 the General Land Office. 



Isogonic Lines in Nova Scotia. 



The table below gives values of the declination in the Mari- 

 time Provinces collected from various sources and from which 

 the isogonic lines have been sketched on the map in plate 26. 

 It must be remembered that owing to the small number of 

 observations, it has been impossible to obtain more than 

 approximate values for the secular change, and so the reduction 

 of the observed values to the present year is only approximate. 

 No attempt has been made to indicate the local variation, since so 

 few reliable observations have yet been made, and so the curves 

 show no irregularities. The map shows, however, the general 

 direction of the isogonic lines in Nova Scotia and is drawn to 

 point out the very great variation in the value of the declina- 

 tion in the province. 



