of the South Magnetic Pole. 105 



14th of August 1642, in his account of the voyage, gives the 

 following particulars of an observation made on the 22nd of 

 November of the same year, when by a prior and subsequent 

 observation of November the 15th and 24th, he was in about 

 latitude 43° S., and longitude from Paris 160°. 



" The needle was in continual motion without resting upon 

 any of the eight points of the compass," which he says, "led 

 him to conjecture that there were some mines of loadstone on 

 that spot." 



Tasman's Journal, written in Low Dutch, is now an ex- 

 tremely rare book : a translation of it is given in Dr. Hooke's 

 Philosophical Tracts, p. 179, for the year 1682; in Nar- 

 borough's and in Correal's Collections of Voyages ; and also 

 by Harris, who gives a new translation of it in the second 

 edition of his Collection of Voyages, where, although he no- 

 tices Dr. Halley's theory of the magnetic poles, which was 

 published in 1683, he does not seem to suspect that Tasman's 

 observation of this very remarkable affection of the magnetic 

 needle was made in the immediate vicinity of the south mag- 

 netic jjole^ at that period in that particular situation, ascer- 

 tained by the horizontal needle only; the dipping-needle, in- 

 vented by Norman in 1681, being then unknown. Dr. Halley 

 was of opinion that the north magnetic pole was not far from 

 Baffin's Bay, and that the south magnetic pole was in the 

 Indian Ocean, south-west from New Zealand; whether he had 

 availed himselfof the observation made by Tasman informing 

 this opinion, does not appear. Euler places the north mag- 

 netic pole for the year 1757 in latitude 76° north, and longi- 

 tude 96° west from Teneriffe ; and the south magnetic pole in 

 latitude 58° south, and longitude 158° west from Teneriffe. 



It has been ascertained by observation, that the magnetic 

 poles were on the meridian of the poles of the earth at London 

 in the year 1657, being fifteen years after I'asman's observa- 

 tions, and that it reached its utmost degree of variation west 

 in the year 1818, when it became stationary at 24° 26' west, 

 and has since in respect of London been retrograding towards 

 the east, completing one quarter of the circle round the poles 

 of the earth in 161 years at the rate of 11 or 12 minutes of a 

 degree in a year ; so that, presuming Tasman was on the south 

 magnetic pole on the 22nd of November 1642, it would now 

 be found in or about the forty-third parallel of south latitude 

 to the south-east of the island of Madagascar, a convenient 

 situation, when compared with that of the north magnetic pole 

 for ascertaining the exact position of the south magnetic pole, 

 and where experiments with the horizontal- and dipping- 

 needles to lead to its discovery and determine the comparative 

 intensity of the south magnetic power might with facility be 



Third Series. Vol.9. No. 52. ^Mff. 1836. N 



