Page:The National Geographic Magazine Vol 16 1905.djvu/104

Rh reported for any part of the bay. At the head of the bay high tide is about 20 feet above mean sea-level. Low tide is as much below. The tidal bore is seen in Maccan River, entering Cumberland Basin ; but it is stronger in Petitcodiac River, entering Shepody Bay. It is best seen at Moncton, where the first pair of views is taken.

Mr Hayward gives the following details:

The Petitcodiac River turns at Moncton from a northeast to a southeast course, then entering the northwestern branch of the bay. The mud flats are three-quarters of a mile wide at Moncton. The retiring tide leaves them covered with ripple-marks. The low-tide view was taken at 10.05 a. m., August 9, 1903, looking easterly. Here the foaming and roaring bore advances against a swift fresh- water stream, rising rapidly. Its height was about 3^2 feet ; its progress was 5 miles an hour. High water, as shown in the second view, is reached about three hours after the arrival of the bore.

The second pair of views was taken at Wolfville, on the eastern arm of the bay near the mouth of the Gaspareaux River, on September 7 and 8, 1903. The piles in the pier are stated to be 60 feet high. The great inconvenience attending so strong a range of tide may be imagined.

It may be well to recall a feature of the Bay of Fundy tides set forth by M. S. W. Jefferson a few years ago in his articles in this magazine, to the effect that the Fundy tides are practically synchronous fiom the mouth to the head of the bay, while the Chesapeake tides, for example, are progressively later and later from mouth to head; but the estuaries at the head of the Bay of Fundy have progressive tides, as in the Petitcodiac. The synchronous "swash" tides of the bay may be easily imitated in a model of an irregular shore on which a shallow sheet of water lies. Tide-like oscillations in the water may be made by an oscillating plunger ; and when the proper period of oscillation is chosen, the tide in a funnel-shaped bay will have small range at the mouth and great range at the head, and the time of high or of low tide will be essentially synchronous all along the bay sides. At the same time a neighboring bay of different form may have progressive tides whose advancing waves may assume the form of a bore if the proper variation of breadth and depth of channel is given.

W. M. D.

O traverse the Sahara from north to south, to join Algeria to the Sudan through the great desert of North Africa, and to subjugate the nomads who wander through that immense region has been one of the principal aims of France in recent years, and one which she has at length attained at the price of long and persevering effort. The hostility of the Touaregs was for a long time an obstacle. Established in the oases scattered over the Sahara, these Berber fanatics and brigands were accustomed to scan the whole desert, and