Tides and Tidal Currents in the Proximity of Land 363 



By eliminating u and v, we obtain the differential equation for // 



It can be mathematically proven that this equation has a solution for an 

 entire area, when the vertical displacement rj or the normal components of 

 the velocity are given for an arbitrary line of demarcation. This is also correct, 

 when this line demarcation separates an ocean from an adjacent sea. In order 

 to solve the problem, the equation (XI. 42) is transformed into an equation 

 of differences, the area under consideration is divided up in small squares 

 and for the centre of each square we establish an equation of differences. 

 The resulting system of equations must then be solved. The numerical com- 

 putation is, however, very laborious. 



