85 
Experiments and Discoveries . 
I 
pass, during the passage of the Hecla and Fury through Lan- 
caster Sound and Barrow’s Straits, perfectly active, where hi- 
therto it has been stowed below as completely unserviceable. 
We must here conclude our account of these important ex- 
periments with the following extract from Mr Barlow’s re- 
port : 
“ The importance of this principle of correction, even for the 
purposes of keeping the reckoning at sea, is sufficiently demon- 
strated in the two cases given by Lieutenants Mudge and Fos- 
ter (pages 75. &81.), where, in the former, the error by the com- 
mon compass course was nineteen miles in latitude, and twenty- 
eight in longitude ; while, by the corrected compass course, the 
error was reduced to two miles in latitude, and four in longi- 
tude ; and in the instance furnished by Lieutenant Foster, the 
error in latitude alone was thirty-five miles in a run of only fif- 
ty, which almost wholly disappeared on the corrected course.” 
“ I am aware,” says the author, “ that seamen depend very 
little upon the reckoning by compass, while they can make the 
requisite astronomical observations ; but as it frequently hap- 
pens that many days may pass without their obtaining such ob- 
servations, it cannot but be of considerable importance to them, 
in such cases, to possess the means of approximating the near- 
est possible to their true place. It is not, however, at sea that 
this method is of greatest use ; it is in narrow channels, in pi- 
loting ships by means of charts and bearings, and in marine 
surveying, that it finds its most valuable application : in these 
instances nothing can supply the place of the compass, and it 
cannot but be important in such cases that its directive power 
should be freed from all irregularity.” 
“ Every reader, whether a nautical man or not, must be aware 
of the great amount of error, and fatal consequences, which 
might arise in a few hours to a vessel in the channel, in a dark 
and blowing night, having for its only guide a compass subject 
to an error of 14 degrees in opposite directions at east and west, 
the very courses on which she would be endeavouring to steer ; 
and who can say how many of the mysterious wrecks which have 
taken place in the Channel are to be attributed to tins source of 
error, of which the most recent, that of the Thames, Indiaman, 
is a serious example. This vessel, besides the usual materials. 
