NO. 15.] EXPLANATION OF THE DEAD-WATER PHENOMENON. 115 



The long and deep Norwegian fjords with no strong tidal currents, 

 obviously offer excellent opportunities for the river-water to spread without 

 mixing as a layer of gradually diminishing thickness, on the top of the salt- 

 water. Furthermore, they are to a large extent navigated by sailing-vessels 

 (and some of them by towed lighters), which as already mentioned, are 

 particularly susceptible to the influence of dead-water. Norwegian seamen 

 therefore become well acquainted with the phenomenon and easily recognize 

 it when meeting it in foreign seas, as well as on their own waterways. On 

 the other hand, a man who meets it once or twice and has not heard of it 

 before, will not be likely immediately to think that he has to do with a quite 

 new and obscure phenomenon; but he will if possible, put it down to the 

 effect of simple and easily explainable causes, such as e. g. currents, whirlpools, 

 muddy water etc. This is so much the more plausible because in many 

 cases, someone or other of these cases has actually contributed its share to 

 the dead-water effect. 



It is therefore probable from the seamen's accounts and the experimental 

 investigation conjointly, that dead-water occurs strongly and particularly often 

 in the Kattegat, the Norwegian fjords and in the arctic regions, as well as at 

 some river-mouths in different parts of the world, and that under favourable 

 circumstances it may occur everywhere where fresh-water flows out over the 

 sea. On looking through the collection of accounts of dead-water beyond 

 Scandinavia (in Chap. 1 and in the Supplement), it seems highly improbable 

 that they should supply a complete and correct representation of the geogra- 

 phical distribution of the phenomenon; on the contrary, the places mentioned 

 in this collection more probably represent just the few cases which have 

 by chance come under notice. It is to be expected that when the pheno- 

 menon has been more generally noticed, we shall soon get a fuller knowledge 

 of its occurrence in different parts of the world. 



F. EMPIRICAL LAWS OF RESISTANCE IN DEAD-WATER. 



Influence of the difference of spec, gravity between the water-layers; 

 the different causes of resistance. 



Fig. 1 PI. XI shows different curves of resistance for the larger Fram- 

 model (1 : 100). The lowest curve refers to homogeneous water. The other 



