The cover of IM is a bows-on view of the 74 gun third rate Worcester leading a line of ships on the larboard tack. The perspective is a bit misleading, like a telephoto lens. At first glance, the officers appear to be on the forecastle, but they are actually aft on the quarterdeck, Capt Aubrey on the windward side is wearing his hat athwartships, and several officers are grouped near the lee rail. A signal hoist far aft is perhaps related to a course change, as the Worcester is sailing closer to the wind than the trailing ships. Two of the other figures in the picture are apparently taking a moment of ease in the head.
Included in the details along the side of the vessel are the bowsprit and spritsail yard, the boomkin pointing somewhat downward, the cathead, a bower anchor attached to a cable (cable-laid), the sheet anchor, gunports showing the lines that will open the lids, and far aft a cutter swinging from the davits.
The most prominent sail is the fore course, with parts of the foretopstaysail, foretopsail, maintopsail, and spanker also showing. Across the forecourse are two rows of short pieces of line; these are the reef points for shortening sail. If the wind increases, the sail can be partially furled, or reefed, to reduce the sail area. In stronger conditions, the lower row of reef points is used to 'double reef' the sail. Some sails, such as topsails, might have a third row.
The lower corner of the sail is the starboard clew. When sailing on the larboard tack, this clew is hauled aft by the sheet. Leading forward from this same clew is a pair of lines called the starboard tacks. They are currently slack, and if you trace them carefully, you will see that they are attached to the boomkin in the bows. If the ship were to come about onto the starboard tack, the starboard sheet would be eased, the foreyard braced around, and the starboard clew hauled forward by the tacks. Throughout the canon, Jack sometimes refers to sailing with the starboard tacks aboard. This is just another way of saying sailing on the starboard tack.
Above the tacks is another slack line leading forward and attached to the side edge of the sail by a bridle arrangement. Just as the tack is used to pull the lower corner of the sail forward when sailing close hauled, this 'bowline' is used to pull the windward side of the sail forward, to keep it from flapping or 'luffing'. And this is what Jack means when he says the Surprise is sailing on a bowline - as close to the wind as possible.
© Don Seltzer