[DAWSON] SECONDARY TIDAL UNDULATIONS 23 



amplitude as this, they would be quite apparent at any time of tide, even 

 where the range is as great as at St. John. 



We will not venture to discuss at present any theory for the explanaT- 

 tion of these undulations, as our purpose here is merely to place on record 

 a remarkable example of them. It seems fairly evident however, that 

 these undulations occur chiefly at times of storm disturbance ; and 

 possibly in the present instance, they may be due in part at least to the 

 inter-action of different storms. 



In any theory which may be put forward, a carefal distinction 

 should be made between the originating cause of these undulations, and 

 their progress or transmission from one locality to another when once 

 they have been produced. So far as transmission may take place, the 

 examples here given appear to indicate that these undulations do not 

 become magnified in their range, in the same ratio as the main tidal 

 undulation itself does, under the influence of the general features of the 

 coast. The percentages in the above list, have been given with reference 

 1 1' this question. It may also be noted in this connection, that in estuaries 

 ^^ here the tide itself increases to the greatest range, as in the St. Lawrence 

 below Quebec and towards the head of the Bay of Fundy, secondary 

 undulations are entirely absent ; while on the other hand they are often 

 most evident and persistent where the tide itself has so little range as 

 to be almost effaced ; as for example at the Magdalen Islands in the 

 middle of the Gulf of St. Lawrence. 



For the study of the interesting problem which these secondary 

 undulations present, it is unlikely that better conditions exist anywhere 

 than on the eastern coasts of Canada. In the region extending from 

 Quebec to Halifax, and from Yarmouth to the Strait of Belle Isle, the 

 tides range from the highest in the world, to so flat a tide as to be almost 

 inappreciable except at the springs ; and there is thus scarcely anything 

 left but these undulations and the effect of storm disturbance. In this 

 region, eight principal tidal stations have been established by the Tidal 

 Survey, which is carried on under my direction by the Department of 

 Marine. From these stations, simultaneous tidal record of two to four 

 years has now been obtained ; accompanied by meteorological returns 

 from ten places in the region, and supplemented by a complete file of 

 daily weather charts showing the isobars, issued by the Meteorological 

 Service. At three of the tidal stations themselves, barograph records are 

 also secured. The monthly charts issued by the Hydrographie Ofiice 

 of the United States, which show the tracks of all the important storms, 

 are also available for purposes of comparison. In addition to the prin- 

 cipal stations, fifteen secondary stations at different points in the region 

 have now been in operation for periods of three or four months during 

 the summer season ; and from these, simultaneous tidal comparisons have 

 been obtained on recording gauges. 



