Why does the Bay of Fundy have such high tides?

We are told that there may be two reasons why the tides which sweep up the Bay of Fundy in Nova Scotia are the highest high tides in the world. First, the bay is shaped somewhat like a funnel and the sweeping waters are forced to pile up deeper as the tide rushes in. This would account for higher tides than normal. But we suspect that another factor adds to the depth of the water.

Certain areas of the ocean form natural basins 3n which the water tends to rock up and down, first one side, then another. The Bay of Fundy is at the extreme edge of such a huge basin and, quite apart from the tides, here the ocean water tends to rise and fall about every 12 hours. This heaving circle corresponds more or less with the tidal cycle and the two factors may work together to make 50 foot high tides at the head of the Bay of Fundy.