NAVIGATION. 
North East;” « South, South West,” and 
“ West, South West “ South, South East,” 
and “ East, South East.” 
In Plate IX. Miscel. fig. 9 and 10 , we 
have given figures of a compass and com- 
pass-card, according to the mariner's ar- 
rangement just described, in which only the 
initials are shewn: the North point being 
distinguished, as it always is, by a fleur de 
lys, or some particular indicial ornament. 
For further particulars, see BIariner's 
comjiass. 
We have been the more particular in 
describing the formation of the compass 
card, because a perfect knowlege of that 
important aid is indispensably necessary 
for all who attempt the study, or follow the 
practice, of navigation. Under the head of 
Magnetism we have explained the proper- 
ties of the load stone, and spoken of the dip of 
the needle, as well as of the variation which 
exists between the true and apparent polar 
directions ; as indicated by the compass. 
Therefore we shall briefiy observe, that 
variation is either Easterly, or Westerly; 
and, whenever it prevails, must be com- 
puted in the reckoning; always making 
allowance for the difference, and laying 
down the ship’s course accordingly. Thus if 
a ship sails due North, and that six degrees 
of Western variation ait: known to prevail 
in that part, where the vessel is sailing; 
instead of sailing due North, as indicated 
by the compass, the vessel must sail six de- 
grees more Easterly, or, in other words. 
North half East, i. e. half a point Easterly 
ofNorth, in which direction the true North 
point would be found by observation of 
the heavenly bodies. Currents must also 
have allowance made for them according 
to their bearing, or the points to which 
they run: it is self evident, that if such 
were not duly ascertained, and set off from 
the dead reckoning, the ship’s place would 
never be accurately laid down, and destruc- 
tion w'ould inevitably follow the neglect. 
The way, or distance, the ship sails-with- 
in the day, is ascertained by means of a 
small piece of board called the Log (which 
see), that being fastened to a thin,' but 
stout line, and lowered over the stern, oc- 
casions the line to run off' from a large reel. 
The line being marked at certain distances 
with small pieces of string, whereon, one, 
two, three, &c. knots are made, at dis- 
tances corresponding with the rate per hour, 
and tire persons who superintends the pro- 
cess, having a minute, Or a half minute 
glass; the lug is allowed to run the line 
from the reel, during such interval; the 
number of knots, on the proximate string, 
indicating the number of miles the ship 
sails within the hour. Hence the techimcal 
term of so many “ knots per hour or “ an 
eight knot breeze,” &;c. 
The whole world is supposed to be com- 
prized under a circle, which in every direc- 
tion, contains 560 degrees of equal mea- 
surement. Such as pass through the meri- 
dian of any place, and from North to South, 
cutting the equator at right angles, are call- 
ed meridional lines, and aie each divided 
into nine degrees, counting from the line to- 
wards the poles respectively: those pro- 
ceeding to the North are called degrees of 
North latitude; those towards the South 
being called degrees of South latitude. In 
this respect all civilized nations are agreed ; 
but in their estimation of longitude, they 
generally differ, each taking some parti- 
cular point within their own dominion* 
as zero, and counting 180 degrees East, 
and as many West ; calling the former East 
longitude, the latter West longitude. Con- 
sequently the union of those adverse desig- 
nations takes place at the antipodes of the 
zero from which they proceeded ; and the 
moment a vessels passes 180 degrees, either 
way, she enters upon 179 of the opposite 
semi-circle, and reckoning the degrees of 
latitude are equal from the equator to the 
pole; and each in general measures about 
69j of British statute miles. But the de- 
grees of longitude vary greatly ; decreasing 
regularly from the equator to the poles, 
where tliey all meet and are as it were an- 
nihilated. The regular declension of the 
circles of longitude, which are the same 
as parallels of latitude, may be seen under 
the head of Dialling ; where in the con- 
struction of lines of latitude, their gradual 
decrease is fully e.xhibited : see also Lon- 
gitude, for a table of longitudes in va- 
rious latitudes. 
A rhumb-line is a right line drawn from 
the centre of the compass to the horizon, 
and is named from that point oftlie horizon 
it falls upon. The course is the angle which 
any rhumb-line makes with the meridian, 
and is sometimes reckoned in degrees, and 
sometimes in points of the compass ; so tliat 
if a ship sail upon the second rhumb, or N. 
N. E. the course is 22“ 30', and so for any 
other. When a ship makes a direct course 
from one point or port to another, and that 
there is no current nor any variation of the 
compass, she sails “ on a rhumb ;” that W 
she i* guided invariably from one to tl 
