National Geographic : 1898 Sep
ATLANTIC ESTUARINE TIDES 405 and so far the ranges are still increasing. The larger rivers are interrupted by rapids at the fall line before the ranges diminish, usually close to the highest station observed. ST LAWRENCE TIDES The St Lawrence is an excellent example of a tidal estuary, and it is to be desired that more and more reliable data may some day be forthcoming for its study. For the present purpose we must exclude the portion of the so-called river between Pointe des Monts and Anticosti, where the tides are unexplained. The " bay " and river remaining are 283 miles long and 40 miles wide at the mouth. When high water has reached Three Rivers a second high water appears at the east end of Anticosti. The bay includes the waters between Pointe des Monts and Isle Royale, whence it is river to Three Rivers. The U. S. Tide Tables give 22 stations here, from which a table has been prepared as before. St Lawrence Tides 0 I II III IV V VI VII VIII IX H.W. interval from Pointe des Monts. 0 125 30 26 21 23 14 17 13 14 H. W. advance in last hour (miles). 9.2 12.9 13.3 14.4 13.9 13.3 11.0 8 3 2 Mean tide range (feet). h. m. m. h.m. h. h.m. h.m. h. . . . . h.n . . . m. h.m. 620o555475335305115105105755Durationofrise. 65630638652655714715715718720Durationoffall. During the first four hours the tide travels up the bay with lessening speed, while the tide range steadily augments; then the advance is irregular and the range diminishes. At Three Rivers, the head of observations, the rise of tide lasts 5 h.; the fall, 7 h. 25 m.-not a strong steepening of the wave front after 283 miles of travel. This may be due to the great depth of the St Lawrence. The Penobscot is in these respects comparable. The Bay of Chaleurs, a hundred miles long and twenty miles wide at the mouth, affords a good bay, the ranges mounting up from 4 feet to 7.6 feet and high water being delayed. There are but nine stations in the tide tables, which rather hint at the facts than elucidate them. It is clear that the tide-wave advances with its front looped deeply into the bay, as is probable with the St Lawrence and all deep bays.