VI 



2) It was thought that the original accounts would best give a clear and 

 complete picture of the phenomenon in its different aspects. Parts of Accounts 

 Nos. 1, 5, 6, 8, 9, 10, 13 may be specially referred to in this respect. 



In some of the accounts desirable rearrangements and alterations in form, 

 have been made, but in every case, I have endeavoured to render the sub- 

 stance as exactly as possible. Statements, apparently having no particular 

 import have been omitted. Of the narrators' own explanations of the phe- 

 nomenon, their means of getting rid of it, etc, only a summary is given in 

 the collective description. A mile, when the contrary is not expressly stated, 

 always denotes an English nautical mile (= 1852 m.); all other measurements 

 are reduced to the metric system. 



Some parts of Chapter II on matters bearing on the subject, are merely 

 a summary from other books and are inserted only for the convenience of 

 the reader. A brief account of Sir John Scott Russell's experiments on 

 phenomena in canal navigation, which are remarkably analogous to "dead- 

 water", is found in this chapter. It is interesting to notice here, that from these 

 phenomena and Lord Kelvin's and Sir G. G. Stokes' mathematical treatment 

 of them and of waves in the boundary between two liquids (see p. 139 and 

 p. 41), it would be but a short step to anticipate that waves in the salt-water 

 fresh-water boundary should cause effects quite similar to those here recorded 

 of "dead-water". It would, however, owing to the small difference of specific 

 gravity between the two water-layers, be rather difficult to believe a priori, 

 that the effect should prove so powerful as it actually is. 



The experiments, although simple typical conditions were selected so as 

 to allow of a simple discussion, were so carried out as to imitate as closely 

 as possible on a small scale, real cases. A model of the Fram and some 

 other boats, were towed in a glass-tank filled with homogeneous water or 

 having water-layers of different specific gravities. The towing force and the 

 velocity of the boat-model, were registered; and one of the water-layers being 

 coloured, the wave-motion at their common boundary could be observed and 

 photographed. 



The experiments thoroughly confirmed Prof. V. Bjerknes' opinion: the 

 vessel when moving at low speeds generated large waves at the salt-water 

 fresh-water boundary, and the resistance at these speeds was anomalously 

 increased. At higher speeds, however, the waves disappeared and the resi- 



