While the snow and the brig might appear closely related, this is in fact not the case.
The two rigs developed from different directions, the brig evolving from the generally smaller brigantine, and the much older snow evolving from the larger three-masted ship.

The most visible difference between the brig and the snow is the latter's "snow-mast", stepped directly behind the main mast.
In contrast to the brig, where the gaff and boom attach directly to the main mast, a snow's gaff, and in later times, its boom, were attached to the snow-mast.
The use of this characteristic snow-mast offered several advantages over attaching the gaff directly to the main mast.

The yoke (or jaw) of the gaff and the lacing of the gaff sail on a snow could move freely on the snow mast, 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, as they typically did.

However, in the late 18th century, brigs started to set main courses as well, which gave rise to the term snow-brig.
The differences lessened even further when the snow-mast was replaced by a steel cable, at which point the term "snow-brig" gradually became interchangeable with the term "brig" and the term "snow" fell in disuse.

The twin brigs Lawrence and Niagara, American warships which participated in the Battle of Lake Erie in 1813, were both snow-brigs.
While the snow and the brig might appear closely related, this is in fact not the case. The two rigs developed from different directions, the brig evolving from the generally smaller brigantine, and the much older snow evolving from the larger three-masted ship.
The most visible difference between the brig and the snow is the latter's "snow-mast", stepped directly behind the main mast. In contrast to the brig, where the gaff and boom attach directly to the main mast, a snow's gaff, and in later times, its boom, were attached to the snow-mast. The use of this characteristic snow-mast offered several advantages over attaching the gaff directly to the main mast.
The yoke (or jaw) of the gaff and the lacing of the gaff sail on a snow could move freely on the snow mast, 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, as they typically did.
However, in the late 18th century, brigs started to set main courses as well, which gave rise to the term snow-brig. The differences lessened even further when the snow-mast was replaced by a steel cable, at which point the term "snow-brig" gradually became interchangeable with the term "brig" and the term "snow" fell in disuse.
The twin brigs Lawrence and Niagara, American warships which participated in the Battle of Lake Erie in 1813, were both snow-brigs.
Snow (ship)