Note 5 — Chapter IV · ToC
Reading edition
A snow was a vessel with three masts resembling the main and foremast of a ship with a third and small mast just abaft the mainmast, carrying a sail nearly similar to a ship's mizzen. The foot of this mast was fixed in a block of wood or step but on deck. The head was attached to the afterpart of the maintop. The sail was called a trysail, hence the mast was called a trysail-mast. (Moore's Midshipman's Vocabulary, 1805.)