NO. is.] EXPLANATION OF THE DEAD-WA TER PHENOMENON. 1M 



incomparably greater velocity than a vessel in dead-water; and the only possible 

 explanation is therefore, that the oscillations depend upon boundary-waves. 



There is another observation (see account No. 8), which is in remarkable 

 accordance with the above explanation of the dead-water stripes: they draw 

 nearer to the vessel or farther off, according as her speed is slowered or in- 

 creased. The reason is that the wave-length must be increased at the same 

 moment as the vessel's speed (compare pp. 35—36), i. e. the distances from 

 the vessel to the wave-crests, grow longer. It is further mentioned, that the 

 stripes remain on the water, when the vessel has got rid of the dead-water 

 and is sailing from them; it is obvious that it should be so, if the stripes 

 depend upon waves which continue to move at their own velocity even after 

 the force generating them has ceased to operate. 



Several observations, although described in different ways, obviously refer 

 to the above mentioned dead-water stripes. For example: "a system of sharply 

 defined, but small waves generated on each side of the vessel" (account No. 5; 

 Fig. 11 PI. IV); "a number of small whirl-pools (eddies) are seen in the 

 boundary between the 'ice-floe' and the water outside it" (account No. 7); 

 "the ship was followed by two sharply defined wakes, the one slightly curved 

 to the port side and the other more strongly bent to starboard" (account 

 No. 13). Perhaps the following descriptions also indicate dead-water stripes: 

 "A line of distinction can often be observed between the dead-water round 

 the ship and the 'living water' outside" (account No. 9); "the water round the 

 ship was somewhat stripey" (account No. 11); "it was as if a floating spar 

 were lying fair across the vessel's stem" (account No. 37); "I saw a long 

 stripe stretching from the bow far over the water on each side, dividing the 

 water into two parts etc." (account No. 38). In the last-mentioned case it is 

 said that the vessel (30 m. long) required 5 or 6 minutes to pass by the stripe, 

 which would hardly be possible if the stripe had been fixed in space; on 

 the other hand it might have been a couple of dead-water stripes which 

 gradually dropped astern, when the vessel got rid of the dead-water. 



It often happens that the dead-water stripes are asymmetrically 

 arranged or that one stripe only, is seen to the one or to the other side 



under different circumstances, such as different depth of the surface-layer, and so on. 

 It would however, lead far beyond reasonable limits, if I were to try to thoroughly 

 clear up this and several similar details. 



