366 On the Insulated or Safety Compass. 
disturbed by the contiguity of small pieces of iron, such as have 
been liable to disturb the mariner’s compass hitherto, and have 
often led to the loss of much property and many valuable lives. 
This discovery seems capable of further extension ; for the needle 
can be protected from the influence of large masses of iron, or 
even from the /oca/ attraction of all the iron in a ship:—but this 
eannot be effected without considerable expense, and it would 
not be of general utility; whereas the protection of the needle 
from the influence of small pieces of iron must be always useful, 
and afford great comfort to those intrusted with lives and pro- 
perty when navigating in narrow seas or dangerous situations. 
Capt. Dunbar, an experienced seaman, who was many years a 
master in the royal navy, and now commander of the Brassa, 
lately arrived from Smyrna, had one of the insulated compasses 
in that vessel during the voyage, of which he writes in the highest 
terms in a letter to Mr. Jennings, stating that it was, not at- 
tracted by iron, although part of the frame, beams, bitts, cables, 
and cargo of the Brassa, consisted of iron. During his stay at 
Malta, Admiral Penrose sent for the compass, and tried it against 
a large magnet which would lift forty-two pounds of iron by its 
attractive power, but it did not influence the compass materially. 
This circumstance induced the Admiral to say, he deemed it the 
most important invention that he had ever seen. 
His Majesty’s ship Isabella had one of the insulated compasses 
on board during the late exploration of Baffin’s Bay, which ob- 
viated the effects of the local attraction of iron, although the 
needle of that compass was not so perfect as those at present 
constructed by Mr. Jennings, the result of experience and atten- 
tive observation. ‘The ships which have lately sailed again for 
Baffin’s Bay have been supplied by him with a great number of 
magnetic needles on a new and peculiar construction, from which 
it will probably be proved, that the needles which unite the figure 
of the horizontal and dipping needle, are those most proper for 
the purposes of navigation ; and by the others, we may expect 
to gain more knowledge of the laws which govern the magnetic 
fluid, because in those regions it appears to act with increased 
energy, as if flowing from the immediate theatre or focus of mag- 
netism. Several of these instruments I have seen; and the in- 
ventor, in the most candid and unreserved manner, gave me a 
satisfactory explanation of their principles,—which has convinced 
me of the wonderful fertility and originality of Mr. Jennings’s 
mind; and to several experienced officers of the royal navy, 
and of the East India Company’s service, as well as to myself, 
his inventions appear to be highly deserving of public encourage- 
ment ; and it is to be hoped that the intrinsic value of the insu- 
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