S4 ROYAL SOCIETY OF CANADA 



throughout its course. The proportion of the variation in the difference 

 which is due to this cause, appears therefore to be relatively small ; and 

 the greater part of the variation is probably occasioned by wind disturb- 

 ance, which in so long an estuaiy is much felt. 



If, therefore, the outstanding error in the time of high water as found 

 by the method of constant difference from Quebec, is due to meteoro- 

 logical causes, the average difference from simultaneous observ^ations as 

 above, is the best result that can be arrived at ; and it is onl}^ necessary 

 to determine further differences for intermediate places with reference to 

 these principal stations. In the actual result, the maximum error will 

 rarely exceed the semi -range in the difference as above given. Although 

 this may amount to as much as 42'" at Anticosti, it decreases towards 

 Quebec ; and thus as the tides become higher and more definite the error 

 is less. It is, therefore, the more allowable to use constant differences for 

 the determination of the time of the tide throughout the whole estuary 

 from Quebec to Anticosti and Gaspé. Also, as the difference does not 

 vary in accordance with the synodical month, it is allowable to assume 

 that throughout the course of the month it will differ little from the 

 difference in Establishment. For intermediate places in this region, the 

 differences in Establishment from the Admiralty list, compared and 

 checked by the differences at Father Point and Anticosti, have therefore 

 been made use of in the mean time as tidal differences from Quebec. 



This regularity of the tides in the Lower St. Lawrence is the more 

 remarkable when compared with their character at the Gulf entrance 

 and throughout the Gulf. The tides in this region are specially impor- 

 tant in relation to the strong tidal currents of the Lower St. Lawrence ; 

 but systematic observations to ascertain this relation have not yet been 

 made. 



In the Strait of Belle Isle, the tide and the tidal currents are fairly 

 regular when undisturbed by the wind ; but during heavy winds the tide 

 is liable to be from 1^ to 2 hours early or late ; and this is also accom- 

 panied by an appreciable difference in the elevation of mean sea level 

 during several successive tides. The tide is chiefly important in its rela- 

 tion to the tidal currents in the strait ; as it appears to have relatively 

 little effect on the Gulf tides in general, compared with the main tide 

 which enters by Cabot strait. 



It was expected that a constant difference could be obtained between 

 the time of high water in the Strait of Belle Isle, and the Atlantic tide 

 at Halifax. But in making the comparison it was found that the range 

 in the difference of the time of high water was very nearly as great as 

 the variation in the luni-tidal interval itself. The following comparisons 

 are based upon one year's observations, from September Ist, 1895, to 

 September 26th, 1896 ; and in both cases the figures given are found by 

 omitting the ten highest and the ten lowest values, and taking the average 



