This great event was preceded by the general Portu- utilization in Europe of the polarity of the magnetic guese ex- needle in the construction of the mariner's compass.
The application of this property to the construction of the mariner's compass is obvious, and it is in connexion with navigation that the first references to it occur '(see' Compass).
It is also more particularly applied to a mathematical instrument ("pair of compasses") for measuring or for describing a circle, and to the mariner's compass.
The mariner's compass during the early part of the 19th century was still a very imperfect instrument, although numerous inventors had tried to improve it.
On the other hand, it has been contended that a knowledge of the mariner's compass was communicated by them directly or indirectly to the early Arabs, and through the latter was introduced into Europe.
