The elusive history of the magnetic compass has many points in common with that of the mechanical clock.
In two important discoveries they long preceded Europe; namely, that of the magnetic compass and the use of gunpowder.
The needle of a magnetic compass serves very well as a magnetoscope.
An arc of the horizon, intercepted between the point of the sun's rising and the east point of the magnetic compass.
(Test this by holding a magnetic compass in different portions of a magnetic field).
This is much more accurate than a magnetic compass, and it keeps the ship on its course.
Our course from here will be due east, or by magnetic compass east by south as near as possible.
The magnetic compass has been for ages the mariner's guide over the trackless waters.
The magnetic compass is not reliable in a submarine with a hull made of steel.
Thus we have testimony to the importance of these little vagaries on the part of the magnetic compass.