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at Algiers, and 53 south at the Cape, they are also both 

 very distant (and nearly equidistant) from the line of no 

 dip. But while their situation is thus nearly symmetrical 

 in regard to distance from the equator and from the line 

 of no dip, it is much otherwise in respect to the line of 

 least force, which enters the African continent only a little 

 to the north of the Cape of (rood Hope, and at a very 

 much greater distance from Algiers. Now, at the Cape, 

 the semi-annual inversion of the hours of extreme 

 easterly and extreme westerly elongation is a very 

 decided feature, scarcely less so than at St. Helena. 

 When the sun has south declination, the extreme 

 westerly elongation is in the forenoon, and the extreme 

 easterly in the afternoon ; and when the sun has north 

 declination, the converse takes place both in the fore- 

 noon and afternoon. The Cape thus possesses this 

 peculiar character of a magnetically equatorial station. 

 At Algiers, on the other hand, the extreme easterly 

 elongation is, throughout the year, in the forenoon, and 

 the extreme westerly in the afternoon. (Aime : Explor. 

 Sci. de 1'Algerie, 1846, t. ii. p. 218.) Algiers has not, 

 therefore, this character of a magnetically equatorial 

 station ; whilst the Cape has it. Again, at the Cape, 

 when the semi-annual inequality is eliminated, (by 

 taking a mean of the two half-years so that their oppo- 

 site deflections may counteract each other,) the residual, 

 or mean diurnal variation is extremely small, and is such 

 as corresponds to a station very little removed from the 

 line where it would vanish altogether ; whilst at Algiers, 

 the mean diurnal variation has a range of about 7 /0 5 

 (Aime, p. 19), which is little less than at Toronto or 

 Hobarton. Thus, in this respect also, Algiers has the 



