NO. IB.] EXPLANATION OF THE DEAD-WATER PHENOMENON. 99 



and 5) or as "rips" or paths in the water, resembling the boundary lines between 

 currents of different velocities or directions. To explain these observations, it 

 is sufficient to remember that the boundary-waves already mentioned, essen- 

 tially consist in veritable currents, running alternately here in the one and 

 there in the other direction in the shallow surface-layer. Along the slopes of 

 the waves, there will consequently be boundary-lines, where the currents en- 

 counter and part from each other: at the former places the wavelets in the 

 surface become short and steep (hopping); on the other hand, wherever the 

 surface-currents issue in opposite directions, the surface, owing to the rising 

 water, is smooth and unrippled or else has a whirling appearance. 



According to this explanation, the shape of the stripes should be the 

 same as that of the crest-lines of the boundary-waves. To judge from the 

 experiments, the boundary-waves are very high only in the case when the 

 vessel generating them, has a speed somewhat below their maximum velocity 

 ( 2 /3 of it, or more); and in this case their crest-lines are more extended to the 

 sides [as e. g. in Fig. 4, PI. V, see p. 48], than are ordinary ship-waves. It 

 might therefore be expected that the shape of the dead-water stripes should, 

 whenever they have been very noticeable, have been something like this figure. 

 For reasons which have been already mentioned, it cannot however be expected 

 that the descriptions of the dead-water stripes should completely agree with one 

 another, or that they should be in all their details reliable. If we therefore 

 make allowance for some discrepancies, we recognize on the whole, a remark- 

 able similarity between the sketches of the stripes (PL IV), and of the lines 

 in Fig. 4, PI. V. This is particularly true in the case of Figs. 1 and 6, 

 PI. IV and even of Fig. 5, PI. IV; the stripes in Fig. 8, PI. IV apparently 

 follow the transverse waves, while in Figs. 9—15, PI. IV they seem to in- 

 dicate a couple of diverging waves 1 . 



It seems remarkable that in some cases the transverse waves (stripes) 

 are seen, and in other cases the diverging one's. The reason probably is 

 that the propelling force of the vessel — and consequently her velocity — has 

 been comparatively greater in the former cases than in the latter. It is proved 

 by the experiments, as well as by calculations of which a summary will be 



1 It may be added that most of the narrators had no information on the explanation 

 here given; and in the case of all the sketches and descriptions it is impossible, that 

 they could have been influenced by a knowledge of this explanation. 



