TIDAL OBSERVATIONS. 381 



years ia which the moon's declination had attained its maximum and mini- 

 mum respectively. The peculiarity of the tide here gives rise to a consider- 

 ahle number of important compound shallow-water tide-components, which 

 has led indirectly to their evaluation at Liverpool and Ramsgate, through 

 this clue to their probable existence having been found. It is probable that 

 others besides those already found may exist, and of which a further exami- 

 nation of the tide-curve may indicate their periods. The epochs of the tide- 

 components are referred to the meridian of Greenwich, similarly to the pre- 

 viously analyzed tides of Ramsgate and Liverpool. 



Portland Breakwater (Lat. 50°-5 N., Long. 9™-8 W. from Greenwich). 

 S. Speed of semidiurnal 2(y — 7j). M. Speed of semidiurnal 2(y —ff). 



