BEARINGS WITH A "DUMB COMPASS" Large ships have extra compasses especially designed for taking bearings, but on a boat that has only a steering compass, bearings are taken with a pelorus (left). Called a "dumb compass" because it is not magnetized, it consists of two sighting vanes and a circular card divided into 360 degrees—identical to a real compass card. To take a bearing on an object, the skipper turns the pelorus card until, it is aligned with his steering compass, so that north is on the same position on each card. Now he turns the vanes until he can sight the object through them. He reads the bearing on the card through the space beneath the vane nearest the object.
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