A snow (also snaw or snauw) is a square-rigged vessel with two primary masts and a third “snow” mast stepped immediately aft of the mainmast and attached to the mainmast top. The snow mast is what differentiates this vessel from a brig.
The foot of the gaff sail flown from the snow mast can be loose footed or secured to a boom. The snow-mast allows the yoke of the gaff and the luff of the sail to move freely, unhindered by the iron bands that held together the main mast, nor limited by the main yard. The gaff on the snow mast could be raised higher than the main yard and independently of it. The resulting freedom allowed a snow, in contrast to a brig, to fly a main course without complications. When brigs began setting a main course they where referred to as snow-brigs. When the snow-mast was eventually replaced by a steel cable, the term “brig” predominated and “snow” fell into disuse.
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