236 



description of the tides in the bay is given by Maimer in "The Tide", 

 from which the figures herein have been abstracted. The bay ex- 

 tends 170 miles inland and there subdivides into two comparatively 

 small and shallow branches. The entrance to the bay is 85 miles wide, 

 and has a mean depth of 280 feet. The bay gradually narrows to 30 

 miles at the junction of the branches, where the mean depth becomes 

 130 feet. The mean tidal range increases from about 18 feet at the 

 entrance to 40 feet or more at the heads of the two branches, reaching 

 50 feet at spring tides. This is the greatest tidal range in the world. 

 The midchannel currents at the entrance to the bay have a strength 

 of 1}^ knots. The tide tables indicate that high water progresses 90 

 miles in 15 minutes in the deep water in the main part of the bay, but 

 the progress of the tide slackens in the shallower branch channels. 

 The current turns nearly at high and low water. 



The mean depth in the bay may be taken at 240 feet. The corre- 

 sponding wave length of the principal lunar semidiurnal component, 

 M2, is 663 miles (par. 326). The length of the bay is therefore nearly 

 one-quarter of this wave length. As shown in paragraph 346, this is a 

 critical length of a closed canal of uniform dimensions, at which the 

 tides are hmited only by frictional resistance. Wliile the analogy is 

 far from accurate, it affords an explanation for the great tidal range 

 at the head of the Bay of Fundy. 



453. Other examples of the increase in the tidal range in deep chan- 

 nels. — The Gulf of Cahforni a, inside of the peninsula of Lower California, 

 is a deep channel extending inland over 700 miles from the Pacific 

 Ocean to the delta cone at the mouth of the Colorado. The mean tidal 

 range decreases from 4 feet at the entrance to 3 feet in a zone about 

 300 miles up the gulf, and then increases to 22 feet at the mouth of the 

 Colorado. In Cook Inlet, in Southwestern Alaska, a deep, funnel- 

 shaped channel about 200 miles in length, the mean tidal range in- 

 creases from about 12 feet at the entrance to 30 feet at the head. 

 Long Island Sound affords another and often quoted example of the 

 increase in the tidal range in a fairly deep closed channel whose length 

 and depth have the relation which should lead to this increase. The 

 sound has a prevailing depth of 65 feet and a length of 70 miles. This 

 length is approximately one-quarter of the wave length of the principal 

 semidiurnal tidal components at the given depth. The entrance from 

 the sea, at the eastern end, is contracted by a chain of islands, in the 

 passage between which the currents are strong, but these passages 

 are so deep and so short that the currents do not appear to produce 

 any considerable head. Inside the entrance the tidal currents are 

 weak. As is to be expected under these conditions, the tidal range 

 increases from 2% feet at the eastern entrance to 7/2 feet at the western 

 end of the sound. High water travels through the somid in about 

 half an hour. 



