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manner. Whatever be the true theory, we know that ves- 
sels have been lost, and the only plan as yet proposed for 
obviating this danger is a recommendation by Dr. Scoresby 
himself, to place a compass at the mast-head for reference 
in case of suspicion, which is merely tantamount to saying, 
that the disease baffles, for the present at least, all his sci- 
entific skill. Professor Scoresby is wise enough to know 
that the motion of a compass situated on the top of a mast, 
even when masts are forthcoming, which sometimes is not the 
case, would cause the most perfect gimbals to sulk or give way. 
Again, a steam-ship’s funnel is made of iron, which fact con- 
fuses matters more than ever. 
«¢ We make out plainly enough, however, that the more dis- 
tant a compass can be placed from the seat of danger, the more 
trustworthy it becomes in the eyes of the ship’s commander. 
Consequently if, regardless of masts or internal attraction, we 
can have a reference compass always at hand, the binnacle in- 
struments may try any vagaries they please without disturbing 
the ship’s running in the least. Day by day we remark their 
deviation, and make allowances accordingly. 
«< My plan is meant as a simple mode of discovering the 
error to which the binnacle compasses are liable in consequence 
of the ship’s local attraction. 
‘‘1st. Let it be granted that a line may be drawn along 
the keel of the vessel, and prolonged indefinitely astern. 
“Ond. That there exists astern of the ship a point on 
this line where, if we place a compass, the needle does not 
suffer from the ship’s influence, but exhibits the true po- 
larity. 
«¢ Now the difference between the binnacle compass and 
the compass alluded to must be the error we so anxiously wish 
to discover.’ As magnetic attraction decreases as the square of 
the distance, I should say that a compass one hundred yards 
or so astern would not be influenced by the iron of the ship: 
consequently :— 
