Section III., 1897. [ SI ] Trans. E. S. C. 



IV. — Character and Progress of the Tides in the Gulf and River St. 

 Lawrence ; as ascertained by simultaneous observations with 

 self- registering Tide Gauges. 



By W. Bell Dawson, M.A., Ma. B., Assoc. M. Inst. C.E., M. Can. Soc. 



CE., F.E.S.C. 



(Read June 23, 1897.) 



The Gulf of St. Lawrence is a land-locked area or inland sea, inclosed 

 on the northern and southwestern sides by Canadian territory, and on 

 the eastern side by Newfoundland. Including the estuary of the St. 

 Lawrence Eiver, its extent from tide-water at Three Eivers to the Strait 

 of Belle Isle is 940 miles ; and its width north and south is 350 miles. 

 The Strait of Belle Isle, by which it communicates with the Atlantic at 

 its northeastern angle, has a width of 11 miles and a depth of 35 fathoms ; 

 but its main communication with the ocean is through Cabot Strait, 

 between Cape Breton Island and Newfoundland, which has a width of 75 

 miles and a depth of 250 fathoms. A^deep channel, from 60 to 40 miles 

 in width, and with a continuous depth of over 200 fathoms, runs in from 

 the Atlantic through Cabot Strait, and continues completely across the 

 Gulf, passing north of the Magdalen Islands ; it enters the mouth of the 

 St. Lawrence between the Gaspé coast and Anticosti, and continues up 

 the Lower St. Lawrence with a depth which only decreases to 100 fathoms 

 near the mouth of the Saguenay. (See outline Map, Plato I.) This deep 

 channel forms the main avenue which the tides follow. On its south- 

 western side, the water is comparatively shallow ; and ranges only from 

 30 to 50 fathoms in the broad bay formed by the sweep of the coast from 

 Gaspé along New Brunswick and Nova^^Scotia to Cape Breton Island. 

 This broad bay, in which Prince i^]dward Island lies, forms a region in 

 which the tides are relatively much retarded. 



In order to obtain tidal data throughout these regions, seven prin- 

 <;ipal tidal stations have been established by the Tidal Survey, which is 

 being carried on by the Department of Marine and Fisheries, and is in 

 charge of the writer. These stations afford 'the tidal data required in the 

 investigation of the currents ; and serve also as reference stations to 

 which the tides at intermediate places can be referred, by difference in 

 the time of the tide from the principal stations. They have accordingly 

 been placed at positions carefully chosen, so as to be free from disturb- 

 ance due to local conditions. They are furnished with self-recording 

 tidal instruments, working day and night ; and they are provided with 

 heating in winter to secure a continuous record throughout the year ; 

 means are provided to obtain a constant datum level and correct time 



