MAGNETIC EXPERIMENTS. 
55 
giving polarity to needles, so as to render them 
capable of answering the purpose of compasses, in 
an instant. This application of the process in¬ 
duces me to be more explicit on this incidental 
subject, because of its importance to seafaring 
persons. There are instances on record, of the 
compasses of ships being spoiled by lightning *:— 
* In the Philosophical Transactions (val. xi. p. 647.), 
is an account of a stroke of lightning received on a vessel 
in the parallel of Bermudas, which carried away the fore¬ 
mast, split some of the sails, and damaged the rigging; 
and, in addition to these extraordinary effects, it inverted 
the polarity of the compass, so that the north point became 
directed towards the south. This induced the navigators, 
who were not aware of the change, to steer back again, 
supposing that the wind had shifted ; and it was not until 
they were accidentally set right by another ship, that they 
discovered the truth. 
Another circumstance a good deal similar to this, also 
mentioned in the Philosophical Transactions, occurred in 
the year 1748-9, on the 9th of January. The ship Dover, 
on its way from New-York to London, was struck by 
lightning during a fierce storm, which was encountered in 
the latitude of 47° 30' N. and longitude 22° 15' W. On re¬ 
ceiving the shock, the captain, and most of the crew, were 
for a while disabled in their limbs, or by blindness,—the 
main-mast was almost perforated,—the upper and lower 
decks and quick work were stove,—the cabins, bulk-heads, 
and one of the main lodging-knees of the beams were started 
or drove down ; and, among several other singular circum¬ 
stances, the magnetism of all the compasses (four in nunn 
ber) was destroyed, or the poles inverted. 
