SZ A VOYAGE OF DISCOVERY 
the mariner’s compass-card into thirty-two points, 
or rhumbs; and for the sake of greater accu- 
racy these points are again sub-divided into de- 
grees. In the centre of it there is an index, 
gnomon, or nave, that revolves on a pivot, so that 
by knowing the time of the day, the course the ship 
is steering is easily ascertained by turning this index 
towards the sun; for it is obvious that when the 
azimuth or bearing of the sun coincides with that 
point of the dial that is of the same denomination, 
all the other points of the horizon will correspond 
with the respective points of the same name on the 
dial-plate. For instance, at noon, or when the sun 
is due south, if the point of the dial marked south 
be turned towards the sun, all the other points of it 
will be directed to those of the same name in the 
horizon; and that which points towards the ship’s 
head, if the dial is a midship’s, will of course be the 
direction she is going in at that time. I ought to 
observe at the same time, that the dial should be 
adjusted at least every three quarters of an hour, 
to correspond with the motion of the sun in azimuth, 
and whenever the ship alters her course it will ne- 
cessarily require to be adjusted afresh. From these 
different corrections or adjustments being so often 
required, it would seem at first to be rather a trouble- 
some guide, and, when compared with that invaluable 
instrument, the compass, it certainly is so; but under 
the present circumstances, it is, as I have already re- 
marked, an useful instrument. The makers, and if 
I mistake not the inventors of this instrument, are 
Messrs. Atkins and Harris. 
Tuesday, 10th. — The ieaities, és been foggy 
during the greatest »art of the day, so that the 
