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poles, and this difference which is indicated by the angle contained by 

 the astronomic and magnetic meridians, is called the Declination of the 

 Needle ; which difference is not everywhere the same. 



In this Eastern part of America the direction of Magnetic North is 

 about sixteen degrees West of true North ; whereas in British Columbia, 

 it is about twenty degrees East of North ; and this declination is con- 

 tinually changing, to the extent of about five minutes in a year, the 

 North end of the needle now gradually moving towards the West, in 

 this Eastern part of America. 



It is therefore of primary importance that, before using in any sec- 

 tion of the country, its direction be ascertained by astronomic 

 observation. 



It is likewise subject to another change, known as the diurnal 

 variation, which deflects it from its usual course about twelve minutes 

 in twenty-four hours, and must be taken into consideration when using 

 it : the maximum variation occurring about 2 p.m., after which it 

 slowly returns to its former position. 



In these northern latitudes the North end of the needle is drawn 

 downwards, the extent of the inclination varying in different locations 

 even in the same latitude. 



It has been ascertained that the North magnetic pole is situated in 

 about latitude seventy degrees North and longitude ninety-six degrees 

 forty-six minutes West, which is a little North West of Hudson's Bay, 

 and not far from Chesterfield's inlet. 



The magnetic equator, does not correspond at all points with the 

 earth's equator, but it is a curved line, in places a number of degrees 

 from the equator proper. 



On the magnetic equator the needle remains in a horizontal posi- 

 tion ; but in southern magnetic latitudes the South end is drawn down- 

 wards in the same way that the North end inclines in northern magnetic 

 latitude. 



In order to counteract this dipping, and to keep the Needle in a 

 horizontal position, a sliding counterpoise is placed upon most needles. 

 Sliding because, as the instrument, from long use or any other circum- 

 stance, loses its magnetism, the North end dips less. 



