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



water, the pendulum was always inclined aftwards, even when hanging as 

 near to the vessel as possible, and this shows that the water had a stern- 

 ward velocity or else had a forward motion slower than that of the vessel. 

 When the salt-water was covered with a layer of fresh-water and the boat 

 was moving in dead-water, the pendulum if suspended some distance out 

 from the vessel, was inclined aftwards; but if it hung just astern (within 

 2 or 3 cm. aft of the boat and within about 1 cm. of her median plane), the 

 pendulum was drawn in towards the boat, and was only occasionally repelled. 

 Observation of small particles of dust on the surface, gave the same result. 

 On both sides of the vessel the particles were carried aft past the vessel, but 

 immediately astern they followed her. A grain of dust was once noticed 

 which was carried aft past the vessel, and, when about 5 or 6 cm. astern, 

 was sucked in again towards, and continued to follow the vessel. The 

 phenomenon seemed to be analogous to that of the wake following just 

 astern of a vessel even under ordinary circumstances; but in the case of 

 dead-water this forward-moving wake is much more developed. 



According to the above described experiments, the statements that the 

 water appears to be dragged with the vessel, may be supposed to be quite 

 correct; but the area within which the water really follows the vessel, is 

 probably not very wide. If the vessel has a stern broad and bluff, so as to 

 produce a heavy wake, we may expect this area to be comparatively wider 

 than in the case of the .Fram-model, with which the experiments were made. 

 In every case it might, according to the experiments, be sufficiently wide, for 

 a small boat towed astern, to be drawn up. 



Those cases in which it is said that the vessel was partly or completely 

 surrounded by a wide expanse of water dragged along with her, I am inclined 

 to explain as due to an illusion. The accident described by Mr. Kroepelien 

 (p. 20; Fig. 1 PI. V) exemplifies this very well. Behind the two "rips" 

 stretching from the bows, the water is smooth and unrippled ; which is easily 

 explained by the dead-water waves steadily bringing up new quantities of 

 water to the surface. On looking at this large, smooth area steadily following 

 the vessel, and at the agitated boundary-lines between it and the water outside, 

 one might well believe that the whole bulk of water was moving through 

 the sea with the vessel. Such a mistake is so much the easier to make, 

 since the speed of the vesse through water, is very small; further, because 



