APPENDICES TO MR. JONES' REPOT (TIDAL AND CURRENT SURVEY, CANADA.)
INVESTIGATIONS IN THE NARROWS OF RIGOLET, 1923.
[Enclosure 1 in No. 1011.]
APPENDIX A.—TIDAL STREAM VELOCITIES IN THE NARROWS AT RIGOLET.
Average values of Maximum Flood and Ebb Streams during each of the periods indicated ; at a depth of 12 feet.
Velocities and knots per hour.
DURATION OF FLOOD AND EBB TIDAL STREAMS IN MID CHANNEL OF THE NARROWS AT RIGOLET.
APPENDIX A (continued.)
DURATION OF FLOOD AND EBB TIDAL STREAMS OFF SQUARE ROCK POINT—RIGOLET.
NOTE.—On account of interruption in the observations, the best mean values are obtained by taking groups from opposite sides of the month, which are thus balanced, and omitting others.
TIDAL AND CURRENT SURVEY—CANADA.
INVESTIGING THE NARROWS OFF RIGOLET, 1923.
[Enclosure 2 in No. 1009.]
APPENDIX B.—DURATION OF FLOW OF THE UNDERCURRENT IN THE NARROWS AT RIGOLET MID-CHANNEL.
To obtain this information a vane of sheet metal weighted, and suspended by a small wire, was lowered from a reel towards the end of the flood and ebb streams. Thus the direction of the stream at any depth was indicated by the direction of the slope of the suspending wire. Lowering the vane to various depths, careful notes were made of the direction of the current ; and the time of change of flow from flood to ebb or ebb to flood near the bottom carefully determined, and compared with the turn on the surface. The current always turned below first at the beginning of the flood and also at the beginning of the ebb with three exceptions as shown in the table below.
TIME OF TURN OF UNDERCURRENT COMPARED WITH THE TURN ON THE SURFACE.
APPENDIX B (continued).
The relation of the turn of the undercurrent to the turn on the surface thus determined, affords the means of calculating the duration of flow of the former in the flood and ebb periods, with the advantage of more extensive observations taken of the surface streams.
As observed, the average durations of the flood and ebb periods on the surface were 5 hours 37 minutes and 6 hours 44 minutes as laid out in the diagram below. The full line represents the curve of the surface current, and the dotted line that of the undercurrent. As the undercurrent flood began 42 minutes earlier, and the ebb 19 minutes earlier, the duration of the 10 flood period is thus 5 h. 37 m. + 42 m. - 19 m., or 6 hours 00 minute, and of the ebb period 6 h. 44 m. + 19 m. - 42 m., or 6 hours 21 minutes.
(NOTE.—Theoretically a flood and an ebb period equals half of a lunar day or 12 hours 25 minutes. Since the periods, as observed, added together give 6 hours 21 minutes, a good check on the accuracy of the determination is afforded.)