Captain Parry's Third Voyage. 165 



having its position modified, and its directive power reduced by the appli- 

 cation of artificial magnets, Lieutenant Foster found, that the true bear- 

 ing upon which a needle exhibits its minimum variations is the same at 

 Port Bowen as at Woolwich, or about S. 38° E, (or S. 85 W. at Port Bowen, 

 magnetic,) which would almost lead to a conclusion that this is a constant 

 line over all the world. A similar coincidence seemed to obtain with re- 

 spect to the magnetic bearing of the line of maximum variation, which ap- 

 peared to be at Port Bowen N. 66 E., agreeing very nearly with that de- 

 termined in England by Mr Barlow. 



The effect of Mr Barlow's Plate, for correcting the effect of local attrac- 

 tion on board ship, occupied the particular attention of Captain Parry, 

 and it is with much satisfaction that we quote the following high and well 

 merited eulogium on this great invention. 



ts The plate thus placed was now to undergo a severe trial on the ship's 

 arrival in Barrow's Straits and Prince Regent's Inlet, where, from the ex- 

 traordinary increase of dip, and the consequently augmented effect of the 

 ship's iron upon the magnetic needle, the compass had before been ren- 

 dered wholly useless on board ship. Never had an invention a more com- 

 plete and satisfactory triumph ; for, to the last moment of our operations 

 at sea, did the compass indicate the true magnetic direction, requiring of 

 course at times a considerable degree of tapping with the hand merely to 

 relieve the needle from friction. And even at Port Bowen, where the dip is 

 eighty-eight degrees, and the magnetic intensity acting on a horizontal 

 needle extremely weak in consequence, the azimuth compass on board ac- 

 tually gave the same variation as that observed on shore, within the fair 

 and reasonable limits of error of observation under such circumstances. 

 Such an invention as this, so sound in principle, so easy of application, 

 and so universally beneficial in practice, needs no testimony of mine to 

 establish its merits ; but when I consider the many anxious days and sleep- 

 less nights which the uselessness of the compass in these seas had formerly 

 occasioned me, I really should esteem it a kind of personal ingratitude to 

 Mr Barlow, as well as great injustice to so memorable a discovery, not to 

 have stated my opinion of its merits, under circumstances so well calculat- 

 ed to put them to a satisfactory trial." 



The following Table contains some of the principal results respecting 

 the variation and dip of the needle :— <- 



Table of Variations and Dips of the Needle in 1824-5. 



