The "snow-brig" USS Niagara (center) in 1913.
A snow or snaw is a sailing vessel. A type of brig often referred to as a snow-brig, the snow was typically a merchant vessel, but was a common form of sailing rig for small two-masted sloops, especially during the first half of the eighteenth century. The twin brigs Lawrence and Niagara, American warships of the Battle of Lake Erie, were both snows.
Snows carried square sails on both masts, but had a small trysail mast, sometimes called a snowmast, stepped immediately abaft the mainmast. This mast could carry a trysail with a boom, with the luff of the trysail hooped to it. Sometimes, instead of a trysail mast, snows carried a horse on the mainmast, with the luff of the trysail attached to it by rings.
Snow: the largest of all old two-masted vessels. The sails and rigging on the main mast of a snow are exactly similar to those on the same masts in a ship; only that there is a small mast behind the mainmast of the former, which carries a sail nearly resembling the mizzen of a ship.