MANAGEMENT OF SHIPS. 97 



Whenever the tiller, and consequently the rudder, is placed in the same 

 direction as the keel, no eflect is produced ; but if, while the ship is moving 

 forward, the tiller is turned to starboard, the rudder moves to larboard, and 

 the water striking on the ship acts on the rudder, and brings the stern to 

 starboard, while the bow is carried to larboard, and conversely ; if, on the 

 other hand, the ship is moving backwards, and the tiller is turned to star- 

 board, the water strikes the ship from behind, driving the rudder which 

 stands to larboard before it, and hence sends the stern to larboard and the 

 bow to starboard, and conversely. 



In order to explain the action of the sails, we premise the following : 

 Suppose a weather-cock standing on its spindle during a calm, in any 

 direction you please ; for instance, the broad end to the west. Let a south 

 wind now blow gently ; it will turn the broad end before it, until it comes 

 into the same direction with the wind. But if the rod had passed through 

 the middle of the vane, making the parts on each side equal, the wind could 

 produce no effect, its pressure being equal on both ends, and the vane would 

 remain at rest. Let a ship be imagined to be such a vane, and the rod 

 supposed to pass perpendicularly through the centre of gravity, D (pi. 7, 

 jig. 18). Now let a three-masted ship be turned with its bow towards the 

 west, and the wind blowing from the south, or on the larboard, we call this 

 the windward or weather side, and the other the leeward side. If a square 

 sail is now hoisted at the fore-mast, the lower weather clew stretched with 

 the tack, the lee clew with the sheet, the starboard (lee) braces holding the 

 yard in the direction of the sheet, the vessel is said to be on the larboard 

 tack, and the sail has the double effect of turning the ship to leeward on the 

 supposed axis, D, and at the same time of driving it forward in the direc- 

 tion of the keel. Let a jib now be raised on the jib-boom, with its tack 

 fastened to the end of the boom, and the sheet drawn aft, a great power is 

 applied to turn the ship to the leeward, as the jib is further from the line D, 

 and consequently forms a longer arm of the lever. All the sails which are 

 placed forward of the centre of gravity, or of the line D, will exercise this 

 powder to a greater or less degree according to their position ; that is to say, 

 all the forward sails have a tendency to make the ship fall off, or turn before 

 the wind to the leeward. If we now suppose a square mizen-sail stretched 

 forward with the larboard tacks and aft with the starboard sheets, this sail 

 will turn the ship to the starboard, and of course to the leeward, and at the 

 same time driv^e her forward ; but the bow is thus made to stand to wind- 

 ward, and the ship is said to luff, or go to windward. All the aft sails, 

 therefore, drive the vessel towards the wind. If both mizen-mast and fore- 

 mast sails are set, each acting with the same power, they each drive the 

 vessel forwards ; for, since the force on both sides of the axis, D, is equal, no 

 turning either of stem or stern can take place. If the mainsail alone is 

 raised, the tack being forward of the axis, D, and the sheet abaft of the same 

 line, the ship is likewise driven forward without turning. If the fore-sail is 

 braced aback with the larboard or weather braces, while the leeward tack 

 is stretched forward, and the weather sheet aft, the action of the sail is to 

 make the bow rapidly fall off to the leeward, while at the same time it drives 



741) 



