322 



are taken to be the same. That in this instance this theoretical assumption is in sufficiently close 

 agreement \\ith the facts may be regarded as estalilished liy the results of the analysis. 



The values of the tidal constants obtained from the analysis are given in the su))joined table, H denoting 

 the semi-range or amplitude (in feet) and k the epoch or " lag " of a component ; — 



The agreement between the values of the constants in successive months is as close as can be expected 

 and may be regarded as quite satisfactory. 



The zero readings (mean sea-level) for the successive months were found to be 4-37, 3-61, 3-90, 3-00 

 feet respectively. In regard to the last value, it should be remembered that this belongs to the period 

 following the breaking of the wire. It would seem certain that there was an irregixlar change of zero due 

 to shifting of the ship's position in the ice, consumption of coal, &c., and that from these values there is 

 nothing to be inferred. 



As a check on the analysis the initial values for the \-arious components obtained were calculated for 

 h., June 1, 1903, and, with the aid of the Indian tide-predicting machine in the charge of the National 

 Physical Laboratory, a curve was run oft" for the two months June and July. The observed heights for 

 the five days beginning h., July 3, 1903 (astronomical time), have been plotted for comparison with the 

 curve give)i by the machine. The two curves are shown in the diagram on p. 323 opposite. The curve 

 obtained from the observations, where distinguishable from the machine curve, is indicated by a broken 

 line. Crosses mark the observed points. The mean sea-level for the " ol)servation " curve is that given 

 b\- the mean of the five days' heights. 



The agreement over these five days is sufficiently close. It may be noted that where the two curves 

 separate they could in each case be brought much nearer to coincidence by a change of zero, as distinct 

 from the addition of another harmonic term, and that such change of zero, as already pointed out, is to be 

 expected. 



The difterences lietween the observed heights and the machine heights were also obtained for every 

 hour on the following days: June 4, June 19, July 1, July 11, and July 24. The zero in each case is 

 arbitrary, but if the analysis were accurate and complete the difference should lie constant. The actual 

 difterences on these five days, however, would appear to indicate a variation having an approximate 

 amplitude of 5 inches, and possibly of approximately diurnal period. This is not apparent in the 

 comparison curves, and further investigation would be necessary before any conclusion could be arrived at 

 in regard to it. 



With reference to the wind records, there is nothing calling for any special comment in connection with 

 the tides. It is clear that the winds have not sensibly impaired the value of the observations, which 

 would appear to have been taken with great care, and have been found quite .satisfactoiy for the purpose 

 of analysis. 



F. J. Selby, M.A., 1 Tidal Assistants at the National 



December 20, 1906. J. de Graaff Hunter, B.A., J Physical Laboratory. 



