468 BEST FORMS OF RIVER ESTUARIES. 



The best form for a river estuary is, when it enlarges 

 gradually as it approaches the sea, affording free 

 scope for the entrance of the tide, and promoting a 

 regular flow of the waters. Estuaries of this form are 

 said to be generally free from bad bars, * the channel 

 being kept clear by the aid of the fresh water discharge, 

 which being penned up by the flood tide, reinforces 

 the ebb, and so produces an equilibrium. The Thames, 

 the Severn, and the Scheldt, may be cited as examples 

 of the latter form of estuary ; but above all that of 

 the great river St. Lawrence forms the noblest of all 

 examples of this kind. The St. Lawrence has a clear 

 channel for ships of the largest size for over 550 

 miles, as far as Montreal; and the tide ascends the 

 river to lake St. Peters, a distance of nearly 500 

 miles, f Taking it as a whole the estuary of the St. 

 Lawrence may be considered as the most perfect 

 example of a great river embouchure in the world, 

 but its obstruction by ice in winter-time constitutes a 

 serious drawback. 



On the other hand the river Ganges is an instance 

 of a mighty stream losing itself in a swampy delta, 

 traversed by an infinite number of intricate shifting 

 channels, which render it almost inaccessible to ship- 

 ping. The Indus is another river wholly inaccessible 

 for seagoing ships from similar causes. 



The embouchures of all the great rivers, however, 

 exhibit each their own special peculiarities; these are 

 endless in detail, so that it would be both tedious and 

 unprofitable to dwell further upon this branch of our 

 subject; but before proceeding to glance at what ap- 



* Encycl. Brit., gth edit., vol. xx.. p. 576. 



f Norie's Navigation, 2ist edition 1877, p 352 ("Tidal Tables.") 



