It is considered that navigation is generally more advantageous along the Terski shore for two 

 reasons: first, the Terski shore is deeper and there are fewer sub-surface dangers along it; sec- 

 ond, in the neck of the White Sea in winter westerly and south-westerly winds prevail which act as 

 decompressive winds for the Terski shore. To this must be added the fact that the Terski shore is 

 the right-handed shore with relation to the direction of propagation of flood-tide waves which enters 

 the neck of the White Sea from the north. It follows that theoretically (and this is verified by direct 

 observations) the tidal amplitudes are greater on the Terski shore than on the Zimni shore. Thus, 

 the tidal compressions and thinnings are more sharply defined along the Terski shore. As a result, 

 the ice is more broken here and navigation by correct use of tidal thinning is easier. For the same 

 reason, navigation in the ice is more difficult along the Zimni shore than along the Letni shore, 

 other conditions being equal. The influence of the decompressive south winds is felt even more 

 along the Letni shore than along the Terski shore. It must be further noted that, other conditions 

 being equal, travel from the Barents Sea into the White Sea (with use of tidal phenomena) is in the 

 same direction as the propagation of the wave. It follows that during the compressions the vessel 

 will drift along with the ice into the White Sea and during the thinnings the vessel will go against the 

 White Sea into the Barents Sea. The vessel is carried backwards during the compressions and dur- 

 ing the thinning it goes along with the ebb-tide current. 



The speed of propagation of the tidal wave is determined by the equation of Lagrange and Airy, 

 as follows: 



c^ = gp, 

 where g = acceleration of gravity, 



p = depth of water. 



Employing the approximate values for the neck of the White Sea, p = 40 m and g = 10 m/sec^, 

 we obtain 



c = 20 m/sec = 72 km/hr = 39 knots 



The spreading from Barents into the White Sea occurs with approximately this same speed 

 not only for the crest of the tidal wave but also for any point of its form and in particular the point 

 where the flood tide changes to ebb tide, or in other words, the point where the maximum thinning 

 of ice is observed. 



From this it follows that if we could assume that a ship could travel among the ice with a 

 speed of 39 knots, then, while going from the Barents into the White Sea it could continually travel 

 in ice thinned by tidal action. Obviously, we cannot make the same assumption for the case of 

 sailing from the White Sea into the Barents. Thus, the tidal factors are favorable for navigation 

 from Barents to White Sea and are unfavorable in the reverse direction. To the above must be 

 added the fact that navigation from the Barents to the White Sea is more favorable along the Terski 

 shore for the added reason that a gentle permanent current runs from the Barents Sea along this 

 shore while along the Zimni shore, on the other hand, there is a permanent current from the White 

 Sea. It is clear that wind conditions can radically alter the picture presented above. 



LITERATURE: 54, 55, 62, 77. 



343 



