VII 



stance was not affected by the fresh-water layer. These facts and another in- 

 teresting phenomenon observed during the experiments, form the subject matter 

 of Section B, Chap. III. 



In Section E of Chap. Ill, I have tried to show that all other phenomena 

 connected with the dead-water — the appearance of the sea-surface, the loss of 

 steering, etc., may be explained from these boundary-waves. Owing to the 

 small size of the tank in which the experiments had to be made, the ex- 

 planation of all these points could not be experimentally confirmed, and some 

 details will possibly be subjected to modifications in the future. It is hoped 

 that the Article "How to get free of dead-water" (p. 110) will not only be 

 found to be an explanation of the seamen's experiences, but that it will in 

 the light of our present enlarged knowledge of the phenomenon, be found to 

 contain valuable suggestions as to the best means of getting free from this 

 very inconvenient occurrence. 



To make sure of the correctness of the explanation given, it must be 

 proved that the boundary-waves, created, were the essential cause of the in- 

 creased resistance in the experiments; and further that this increased resistance 

 is large enough to explain the effects of the dead-water. The proof of these 

 points is one of the chief objects of the last section of Chapter III. 



The experimental work was performed during the time from the beginning 

 of 1900 to July 1901; the first half of the time was, however, occupied with 

 experiments which now may be regarded as only preliminary. 



The expense of apparatus has been defrayed by the Fridtjof Nansen 

 Fund for the Advancement of Science. The Council of the Stockholm s 

 Hogskola made me a grant for the year 1901, from the Fund to the Memory 

 of the Civil engineer August E. W. Smitt and renewed it for the year 1902; 

 I am glad of here having the opportunity of expressing my warmest appre- 

 ciation of this help. 



Also I desire to place on record my sincere thanks to my revered teacher 

 Professor V. Bjerknes, who has with the greatest interest followed my work, 

 and has on many occasions given me the most important advice. 



Professor Fridtjof Nansen, by an appeal published in several Norwegian 

 newspapers, has rendered me most effective assistance in collecting accounts 

 on dead-water. Dr. S. Almquist, Rector of the Hogre realldroverket i 



