06 Analyses of Books. [July, 



II. Journal of a Voyage for the Discovery of a North-west Passage 

 from the Atlantic to the Pacific, performed in the Years 1819, 

 1820, in his Majesty's Ships Hecla and Griper, under the Orders 

 of W. E. Parry, UN. 



It would be inconsistent with our plan to enter at any length 

 into an analysis of this interesting work ; but there are some 

 parts of it more particularly connected with scientific objects 

 which we have thought would be acceptable to the reader to 

 see briefly stated as notices. It is but justice to observe that 

 Capt. Parry's account of his arduous and perilous undertaking is 

 written in a clear and manly style. ' 



On the T aria t ion of the Magnetic Needle. 



Capt. Parry observed that, from the time he first entered Sir 

 James Lancaster's Sound, the sluggishness of the compasses, as 

 well as the amount of their irregularity produced by the attrac- 

 tion of the ship's iron, had been found verv rapidly, though 

 uniformly, to increase as he proceeded to the westward : this 

 irregularity became more and more obvious as he advanced 

 to the southward. The rough magnetic bearing of the sun at 

 noon, or at midnight, or when on the prime vertical, as compared 

 with its true azimuth, was sufficient to render this increasing 

 inefficiency of the compass quite apparent. 



It was, therefore, evident, that a very material change had 

 taken place in the dip, or the variation, or in both these pheno- 

 mena, which rendered it not improbable that he was making a 

 very near approach to the magnetic pole. He afterwards wit- 

 nessed the curious phenomenon of the directive power of the 

 needle becoming so weak as to be completely overcome by the 

 attraction of the ship ; so that the needle might, now be said to 

 point to the north pole of the ship. It was only, however, in 

 those compasses in which the lightness of the cards, and great 

 delicacy in the suspension, had been particularly attended to, 

 that even this degree of uniformity prevailed ; for, in the heavier 

 cards, the friction upon the points of suspension was much too 

 great to be overcome even by the ship's attraction, and they 

 consequently remained indifferently in any position in which 

 they happened to be placed. 



Captain Sabine afterwards observed when on shore at Prince 

 Regent's Inlet on Aug. 7, for the purpose of making magnetic 

 observations, that the directive power of the horizontal needle, 

 undisturbed as it was by the attraction of the ship, was even 

 here found to be so weak in his azimuth compasses, which were 

 the most sensible, that they required constant tapping with the 

 hand to make them traverse at all. 



At Martin's Island on Aug. 28, the dip of the magnetic needle 

 was 88° 25' 58'", and the variation was now found to have 



