PORT ESTABLISHMENT
3
    It may be noted that half tide or mean tidal level is the mean between the four levels of mean high and low water at springs and neaps.
    The Lords of the Admiralty annually publish Tide Tables for
 Standard Ports in the United Kingdom and other Parts of the
                                             SE_
   UONDON. THAMES DATUM _ TRINITY HlOH WATER_'+ 12-50.
HOLLAND                  PIEL D’AMSTERDAM. A.P. ♦      0-93.  
ENGLISH ORDNANCE DATUM.  MEAN SEA LEVEL AT LIVERTOOL   0 00.  
FRENCH DATUM             MEAN SEA LEVEL AT MARSEILLES. 0. 00. 
BELGIUM.                 ZERO DU DÉPÔT DE LA GUERRE. - 6-50.  
IRISH ORDNANCE DATJM                                 - 7 46.  
1 FOOT         0         SCALE                                
                         5 (O 13 •’EET.                       
                                                              
Fig. i.—Foreign Tide Standards
 World, and this work is the accepted official authority on the subject.
   Port Establishment.—The high velocity of the great primary tidal wave is reduced when, in sailors’ parlance, “it smells land”. Thus in the North Sea it runs at 50 or 60 miles per hour. Entangled in local retardation, and subject to local dis-