Section III., 1899. [ 23 ] Tbans. R. S. C. 



V. — Illustrations of remarkable Secondary Tidal Undulations^ in January 

 1899 ; as registered on recording Tide Gauges in the region of 

 Nova Scotia. 



By ay. Bell Dawson, M.A., Ma.E., C.E. 



(Read May 26, 1899.) 



These undulations are shown in the accompanying plate (Plate I,), 

 which gives facsimile reproductions of the simultaneous record from the 

 self- registering tide gauges at Halifax and Yarmouth, N.S. ; St. John, 

 ]S. B., in the Bay of Fundy ; and St. Paul Island in Cabot Strait, which 

 is the main entrance to the Gulf of St. Lawrence. 



The length of the record shown, is from noon on December 31, 1898, 

 to noon on January 2, 1899 ; a period of two days. The heaviest undula- 

 tions occurred on January 1. The time as shown throughout is Standard 

 time for the 60th Meridian West ; or four hours slower than Greenwich 

 Mean Time ; and the corresponding hour lines at the different tidal 

 stations, thus represent the same moment in absolute time. The vertical 

 scales of height are different at each locality, in accordance with the 

 varying range of the tide. In reproducing the Halifax record, the tide 

 traces have been displaced in height, as noted, to avoid confusion of the 

 lines. 



On the following plates (II. and III) the tracks of storms during the 

 period in question, are shown ; as well as the barograph record at St. 

 John, N.B. The chart of the storm tracks is taken from the "Pilot 

 Chart of the North Atlantic" for February, issued by the United Statea 

 Hydrographie office. It will be noticed that two of the storms rose fully 

 to hurricane severit3^ The unusual undulations of the barometer at the 

 time are also noteworthy, especially on January 1. 



The tide itself in its general progress, arrives first at Halifax and St, 

 Paul Island ; then about two hours later at Yarmouth, and an hour 

 later still at St. John. Its range increases in the same order ; from about 

 5 feet at Halifax and St. Paul Island, to 15 feet at Yarmouth and 25 feet 

 at St. John, at the spring tides. 



With regard to the occurrence of secondary undulations, they are 

 almost continuously present at Halifax at all times, and it is exceptional 

 for the tide trace to be free from them ; but those here shown are unusu- 

 ally heavy. A few days before the date now under consideration, they 

 wei'e also as exceptional ; namel}^, at the high water of December 26^ 

 between 19 and 20 o'clock, when they attained a maximum range of 1-20 

 feet. 



