NO. IB.] EXPLANATION OF THE DEAD-WATER PHENOMENON. 93 



E. EXPLANATION OF THE VARIOUS EFFECTS OF THE DEAD-WATER 



PHENOMENON. 



All the accounts of dead-water, received, agree that the phenomenon is 

 necessarily connected with the existence of a more or less fresh water-layer 

 on the top of the heavier sea-water. It is proved by theoretical and experi- 

 mental investigation above, that a vessel moving in such a place, creates waves 

 in the boundary between the two water-layers, and that on this account, very 

 marked effects on the speed of the vessel will occur; and it will be shown 

 below, that from the existence of such waves all essential effects and pecu- 

 liarities of the dead-water phenomenon can be very simply explained. In the 

 next section of this chapter it will, in addition, be shown that the resistance 

 and speed-reduction due to the wave-generation, is of just the proper order 

 of magnitude to explain the effects of the dead-water; so that the correctness 

 of the explanation may be regarded as completely substantiated. 



If the surface-layer be running as a current on the top of the heavier 

 water below with a velocity of its own, this circumstance will be a contri- 

 butary cause to the loss of steering-power, which may however, often be 

 entirely due to the boundary-waves mentioned above, and quite independent 

 of such a surface-current. 



Several very different theories — more or less impossible or insufficient — have been 

 put forward with the view of explaining dead-water; and it would be to no purpose to 

 criticise them all. One of them may however be mentioned, as it has recently been pu- 

 blished in a well-known journal (Annalen der Hydrographie und Maritimen Meteorologie, 

 1904, Heft. I; "Totwasser", von Kapt. H. Meyer). Kapt. Meyer mentions several cases 

 of dead-water which, as they refer to places from whence I had before only very scanty 

 information, are of great interest here, and I shall therefore permit myself to make 

 an abstract of them in a supplement at the end of this treatise. Finally, Kapt. Meyer 

 presents a detailed explanation of the phenomenon in its various aspects. He explains not 

 only the loss of steering but also the speed-reduction, as due to currents of different direc- 

 tion or velocity: since a ship is resisted by a very great force when moving in an athwart 

 direction, and moves easily, only in the direction of her keel-line, he concludes that she 

 must on the whole be difficult to move, if she stick in two currents of different directions 

 so that motion athwart through at least one of the water-layers, cannot be avoided. "Wenn 

 man bedenkt, dass ein schwimmendes Schiff vermoge seiner Bauart nur in seiner Kiel- oder 

 Liingsrichtung mit verhaltnismassig geringer Kraft durch das Wasser bewegt werden oder 

 solches durchschneiden kann, dagegen in seiner Dwars- oder Querrichtung nur mit grosser 

 Kraft in minimale Bewegung zu bringen ist, so wird es begreiflich, wie schwer es halten 

 muss, ein Schiff vorwarts zu bewegen, das in zwei wagerecht getrennte Wasserschichten 

 taucht, sofern beide nicht die gleiche Richtungsbewegung haben, es mithin keine derselben 

 in seiner Lfingsrichtung durchschneiden kann." 



