16 EKMAN. ON DEAD-WATER. [norw. pol. EXP. 



"In the Moss Sound, in which a rather full river empties itself, dead-water very com- 

 monly occurs, especially in spring and summer time. Skippers of small craft relate that 

 they are often obliged to tow their vessels through nearly the whole sound (about 3 or 4 

 miles) by a rope from shore, even with a nice little breeze of lair wind. Sailing while 

 the dead-water lasts is impossible, if the wind be not fairly strong. 



"Often the phenomenon appears in the manner described below: 



"A small vessel sails free (the wind on her quarter) on the starboard tack for instance, 

 as in Fig. 12, PI. IV. Suddenly a stripe begins to form on the water, issuing from some- 

 where on the windward side of the vessel and stretching obliquely astern (see the figure). 

 Outside (forward of) this stripe the water, as usual, runs aft by the vessel, but inside it 

 the water forms a kind of wake in which the water seems to follow the ship. This has 

 been observed in wind, sufficient to give the vessel about 2 knots' speed. On the whole 

 the phenomenon presents itself to the sailor, as if part of the water separated from the 

 rest, attached itself to the ship, and was dragged by it through the sea '. When the stripe 

 is developed, the vessel runs up into the wind in spite of the helm and lies quite power- 

 less with her sails shivering. By rowing with an oar on the windward side she may be 

 brought off again, and sailing is possible for a short time, but soon a new stripe begins 

 to form and the vessel runs into the wind again. The masters of quite small craft often 

 try to free their vessels from the dead-water by stirring the water with an oar, and it is 

 said they sometimes succeed. 



"Several years ago, while at gun practice in the Kristiania Fjord the narrator, then 

 a lieutenant, was ordered with a gun-boat to tow away two small vessels, which lay be- 

 calmed near each other in the line of firing. One of them was towed away without any 

 difficulty, while the other, though of similar size, got into dead-water, and an extraordinary 

 amount of work was required to get this vessel from the spot." 



No. 7. Mr. G. 0. Nilsen of Bestum near Kristiania has been kind 

 enough to ask several sailing masters for information on dead-water and to 

 send me a summary of the result obtained. From this summary the follow- 

 ing may be cited. 



"If a vessel, sailing with an even breeze at a rate of 3 or 4 knots, enters a zone 

 of dead-water, her speed will be immediately slackened, as if she had struck a reef of 

 mud. The water is seen to follow to a distance of several metres from both sides of 

 the vessel, just as if she had suddenly been enclosed by a large ice-floe. As long as the 

 vessel makes head-way, a number of small whirl-pools (eddies) are seen in the boundary 

 between the "ice-floe" and the water outside it. The eddies produce a bubbling sound. 

 The vessel gradually has her speed stopped and then no longer answers her helm, drifting 

 helpless sometimes even against the wind. 



"If the wind increases, the vessel slowly begins to make head-way, constantly dragg- 

 ing the surrounding water with her. This body of water, reaching 3 or 4 m. before 

 the stem, drops slowly astern, until the vessel has the bow clear of it. Then she begins 

 to get more speed, and the "dead-water" constantly moves aft clinging, at last, to the 

 stern of the vessel and dragged along with it as a float of as much as 20 m. in length. 

 If the wind now decreases, the whole mass of water may rush forward and enclose the 

 vessel once more. If not, the vessel now answers her helm, and after some manoeuvres, 

 all of a sudden, breaks free. 



These details are given with reservation, owing to the uncertainty naturally connected 

 with such an observation when not made carefully, with a conscious and definite in- 

 tention. 



