SURVEYS OF TIDES AND CURRENTS IN CANADIAN 



WATERS. 



Tidal and Current Survey. 



In this survey, substantial progress has been made in the tida^ 

 branch, and the investigation of the currents was continued in the 

 summer season. The D.G-.S. Gulnare was again employed for the 

 purpose, and Dr. W. B. Dawson, the engineer in charge of the survey, 

 gave his personal supervision to this work from June to September. 

 The region chosen for examination was at the entrance to the Bay of 

 Eundy, extending from Grand Manan Island to Cape Sable. 



The currents in this region were an entire contrast to those exam- 

 ined in the previous season, and required a corresponding modification 

 in appliances and methods. They were strong, steady, and deep ; 

 instead of weak and often superficial and easily disturbed by the wind 

 as on the south-eafetern coasts of Newfoundland. There are ocean 

 steamship lines of the first importance which run through these waters ; 

 and this is the first time that the currents on these routes have been 

 systematically investigated with modern appliances. These outer 

 waters are also of greater importance to navigation than the tidal 

 streams in the more restricted part of the Bay of Fundy. It has there 

 the character of an estuary, in which the currents run parallel to the 

 shores; and they have thus little tendency to set a vessel out of its 

 course. At anchorages carefully chosen, the speed was measured by a 

 current meter, and the direction was noted every half-hour, day and 

 night. The observations also included the under-current, the tempera- 

 ture of the water, the mileage and direction of the wind, and a 

 continuous record of the tide on the self-registering gauges at Yarmouth 

 and St. John, N.B., for comparison with the set of the current. 



The under-current was observed by means of a pendulum weight, 

 suspended on patent sounding wire. This was the same in principle 

 as the deep fan used for the weak currents met with in previous seasons. 

 For these stronger currents the design was modified. A length of brass 

 tubing was used, sufficiently weighted, which could be lowered to any 

 desired depth. The direction of the under-current would then be clearly 

 indicated, and its strength became known also from the angle of the 

 wire with the vertical, as measured with a clinometer. The actual 

 velocity of the current corresponding to the various angles of inclination 

 was determined experimentally by comparison with the current meter; 

 but the technicalities of this reduction it will be unnecessary to enter 

 upon. 



