4b Canadian Arctic Expedition, 1913-18 



Survey. In default of this method, the only other way when the observations 

 are not simultaneous, is to refer the time of the tide to the moon's position; 

 so that the various localities may be compared, and the progress of the tide 

 ascertained. The tide is referred to the moon by the luni-tidal interval; which 

 is the interval of time between the moon's transit across the meridian and the 

 next following high water. This interval at the Spring tides, when the moon 

 is new or full, is termed the "Establishment". In dealing with complete tidal 

 ■observations, this interval can be strictly defined; and in the region under 

 •consideration, where the range of the tide is often less than one foot, the time 

 ■of high water is more definite at the Spring tides because the best range is then 

 obtained ; and the Establishment is thus the best time-factor to deal with. 



The other element in the tide is its height or range. This can be determined 

 independently at each locality; and it should properly be referred to a low-water 

 datum, but this was not attempted in these regions. It is best, therefore, to 

 deal with the range of the tide, from high water to low water, which can be 

 directly observed; rather than the rise above a fixed datum level. 



When desirable, the readings on tide scales were plotted, to obtain the 

 corresponding tide curves. This plotting, and the general reduction of the 

 observations, was carried out by Mr. H. W. Jones, of the Tidal Survey staff. 



TIDAL OBSERVATIONS OBTAINED IN 1914 AND 1915. 



Collinson point. — On the north coast of Alaska. Longitude 9 h. 39 m. 19 s. 

 West. — Observations were obtained here in 1914 from January 16 to May 6, 

 by Dr. J. J. O'Neill and Mr. J. R. Cox. As this was headquarters for the winter, 

 the large recording tide gauge was used. There are some interruptions in the 

 above period; but the observations afford the range at six Spring tides and five 

 Neap tides. This range is only 7 inches at the Springs and 3 inches at the 

 Neaps. With so flat a tide curve, the time of high water can only be obtained 

 at all definitely at the Springs; and a value for the Establishment has been 

 deduced, which shows a fair degree of constancy in the circumstances. The 

 results are given in abstract in the table for Collinson point appended. 



The time on the tide gauge record is assumed to be correct throughout. 

 Collinson point local time was used; and although no time errors are noted, 

 it is taken to be correctly kept on the average. 



Martin point. — On the north coast of Alaska, 50 miles east of Collinson 

 Point. — The observations were for three days only, on March 19 to 21, 1914. 

 They were taken by Messrs. F. Johansen and G. H. Wilkins, as readings on a 

 tide scale; the readings being to the hundredth of a foot, or to the nearest 

 quarter of a tenth. A watch was used to carry the time from CoUinson point; 

 but as its error and rate are not stated, the time remains uncertain. As the 

 observations were at the Neap tides, they would not serve in any case for a 

 determination of the Establishment. The only value obtainable, therefore, 

 is the Neap range; which is taken as the mean of four consecutive differences 

 of level, between high and low water, to eliminate inequalities. This method 

 of obtaining the range is used in all cases in dealing with these Arctic tides; 

 and it is justified because of the small range. The Neap range here at this date 

 was 33/^ inches. 



Demarcation point. — ^Close to the Alaska boundary. Longitude 9 h. 24 m. 

 49 s. West. — The time was carried by a watch which was correct when Collinson 

 point was left on April 25, and was 46 minutes fast of Collinson point time on 

 the return from the trip, on May 26. By assuming the gaining rate to be constant, 

 and allowing for the difference of 14J^ minutes in longitude, it is therefore 

 possible to reduce the observations definitely to local time at Demarcation 

 point. 



