183 



Fig. 1. 



1823.] Construe/ ion of Sea Harbours. 



north point, having her bowsprit N, 73° 7' 30" W, she is on the 



starboard tack ; and on the larboard tack, if in the same wind, 



her bowsprit point IV, 73° 7' 30" E. Thus if a vessel sail along 



the line ee, fig. l,tocr, the wind 



blowing in the direction g a, f 



she is on the starboard tack, 



the line d e making an angle 



of 73° 1' 30" with the line g a ; 



and for the same reasons, in 



the same wind, she is on the 



larboard tack, when sailing 



along the line b a. Hence by 



sailing with the wind, or by 



tacking, a vessel can pass 



from any one place to any 



other ; and of course in one way or the ether she approaches a 



harbour. 



As that entrance which presents itself to the open sea, and 

 admits the surf, can be passed by vessels in all winds ; and 

 easier in any wind than the other kind of entrance, I will first 

 treat of it. Let B, fig. 1, be this entrance into the harbour E; 

 D the open sea; A C two piers forming the exterior wall of the 

 harbour; // ta line passing through the middle of the piers ; and 

 g a J' another line at right angles to them, and in the middle of 

 the entrance meeting with the line h i. Now the wind blowing 

 in the direction g d is the most adverse to a ship approaching the 

 entrance B from the open sea ; and, as before shown, b a and c a 

 are the lines of approach for this wind. These lines b a and c a 

 make an angle of 13 points, or 146° 15', with each other; and, 

 being the larboard and starboard tacks for the most contrary 

 wind, they have within them all the necessary lines of approach 

 for winds from all points of the compass ; and the harbour E 

 having in front of its entrance 13 points, or 14b° 15' of clear 

 sea room, is accessible in any wind whatever. 



The directly contrary wind, and winds within a point on each 

 side of it, would be in gales the worst of all to enter with ; but, 

 that coming from the adjoining land, they have not space to 

 raise a high sea' near the harbour ; otherwise a vessel in attempt- 

 ing: to enter against a gale out of the harbour-mouth, would, to a 

 certainty, be driven out to sea again. 



Vessels passing through entrances of this kind can in all 

 winds take shelter within the pier-heads without any assistance 

 from harbour boats to draw them into the entrance, and in gales 

 from any quarter are not, as in entrances of the other kind, in 

 danger of being driven on the lee shore, provided they are in a 

 good sailing condition and come to the proper place to make the 

 entering tack in side winds. But if vessels arriving in distress 

 by violent storms, by negligence, or want of local knowledge of 



