called "bore." Professor G. H. Darwin noted on the banks of the Severn during the spring tide in September, 1897, that there was no proper bore, but only a succession of waves up-stream, and a rapid rise of water-level.
In the case of the River Seine, which has been dyked as far as Rouen to admit vessels of twenty feet draught, it is said that there is a bore (barre or mascaret) at every tide, ranging usually from eight to ten feet. This is probably accounted for by the fact that after Candebec and Quillebœuf, the estuary is set with extensive sand-banks between which flows a narrow navigable channel.
These bores are relatively small compared with that in the Ch'ientang Kiang, while the destructive bore of the great Amazon is robbed of its impressiveness because it can not be well observed on account of its very magnitude; moreover, with it as well as with the other rivers it is only at spring tides and with certain winds that the phenomenon is at all striking. On the other hand, the Hangchow Bore occurs at every tide to a remarkable extent in any season and at certain times assumes colossal proportions and is always easily observable. For comparison it may be interesting to note the following description of the Amazon's bore, or proroca, by La Condamine: