LLNES OF MAGNETIC DECLINATION IN THE ATLANTIC. 
201 
But whenever it may be clone, it may be expected that the observations of that period 
will be much more accordant with each other, and with nature, than those which 
have been at my disposal ; in consequence of the general adoption, that we may 
reasonably anticipate will then have taken place, of the practice of correcting for the 
deviation in the pointing of the compass occasioned by the ship’s iron, and which the 
increased employment of iron in the equipment of vessels and the magnitude of the 
errors occasioned thereby, already render in a great number of instances absolutely 
indispensable. Those who know, as matter of history, the difficulties with which the 
first introduction of lunar observations and chronometers had to contend, can con- 
fidently look forward to a period when the practice of correcting the errors of the 
compass shall have become general amongst naval officers at least, if not, as may be 
hoped, amongst merchant seamen also ; especially since in the form in which the 
corrections are now placed, no other preliminary knowledge is required for this pur- 
pose than that of the four first rules in arithmetic, with due attention to the signs by 
which the errors and corrections are characterised. 
