148 ANNUAL OF SCIENTIFIC DISCOVERY. 



length on the poop and forecastle ; the determination, from time to time, of 

 the polarity of iron bars, standards, &c., having an upright position; and, 

 finally, the ascertaining of the position taken by a Fox's dipping needle in 

 different stations about the deck, and comparing the results with the known 

 terrestrial clip. 



By these several appliances, the whole of the objects contemplated in the 

 voyage were satisfactorily and completely attained ; and to Dr. Scoresby it 

 was necessarily most gratifying to find that not one of the conclusions he had 

 been led to by inductive research was in any measure contravened ; but, on 

 the contrary, all the leading propositions he had for years been urging on the 

 attention of navigators and men of science were distinctly verified. Thus, 

 just as he had predicted, the ship retained her original magnetic condition, 

 and the adjusted compasses preserved very nearly their original state, so long 

 as the ship was on courses not very remote from the direction of the ship's 

 head when building ; but when she came into a south-westerly direction, the 

 reverse of that on the stocks, under a heavy sea, just as had been predicted, 

 the compasses changed, and there was an error, temporarily, in the steering 

 compass, of a point or more. On reaching a position of considerable southern 

 dip, the adjusted compasses went wrong one of them to the extent of a point 

 and three quarters a moderate change only in comparison with many ships, 

 due, no doubt, to the favorable position of the Eoyal Charter's compasses in 

 being removed so far from the stern, and entirely above the iron plating of 

 the sides. On swinging the ship at Melbourne, the standard compass was 

 found to have lost nearly one half of its original errors, and the two adjusted 

 compasses to have attained considerable deviations ; whilst the compass aloft 

 was, to all practical ends, quite correct. But the most striking change 

 exactly consistent with theoretic deductions was the complete inversion of 

 the ship's magnetic polarity the whole of the top sides having changed from 

 southern to northern, externally; and every standard, stanchion, davit, or 

 other mass of iron about the deck, including also four iron capstans, had 

 attained at the upper parts northern polarity, which, northward of the equator, 

 had been tested as having their southern poles upward. Approaching the 

 magnetic equator, on the homeward passage, the two ends of the ship, as had 

 also been predicted, attained polarities corresponding with the action of ter- 

 restrial induction, the stem aloft, as well as below, changing to southern 

 polarity, and the head becoming more intensely magnetic with the contrary 

 polarity. The gradual travelling of the southern polarity, from the stern 

 forward, as the ship advanced northward towards the line, was a fact which 

 Dr. Scoresby watched with great attention and interest, until, after reaching 

 some distance within the northern tropic, the whole of the ship's sides had 

 changed again their polarity, so that from stem to stern, as when the ship first 

 set out, the upper plating had all acquired the southern polarity. Finally, 

 as to these corroborating facts of previous deductions, it was mentioned 

 that, though the upper polarity of the ship had changed, yet some general 

 influence, derived from the previous inversion of polarity, or, more particularly, 

 from the earth's inductive power, while the ship's head was continually directed 

 northward from the passing of Cape Horn, had been received or retained. 



