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TO ASSIST WORK ON THE TIDES. 217 
To Assist Work on the Tides.—Report of Committee (Professor 
H. Lamp, Chairman; Dr. A. T. Doopson, Secretary; Colonel Sir 
C. F. Cross, Dr. P. H. Cowstu, Sir H. Darwin, Dr. G. H. 
Fow.ter, Admiral F. C. Learmonts, Sir J. E. Peraveu, Professor 
J. ProupMan, Major G. I. Taytor, Professor D’Arcy W. 
Tompson, Sir J. J. Tuomson, Professor H. H. Turner). Drawn 
up by Dr. A. T. Doopson, Tidal Institute, University of Liverpool. 
§1. The Committee was appointed to investigate the degrees of accuracy 
obtainable in the analysis and prediction of tides. A great deal of work on 
tidal records has now been done under the superintendence of the Secretary 
at the Tidal Institute, and some definite conclusions on the subjects of reference 
have now been arrived at. These are restricted to short-period tides. 
(1) On the basis of previous methods of harmonic analysis and prediction 
the errors of prediction for certain British stations may amount to more than 
a foot, apart from errors due to the use of predicting machines. At these 
stations the range of tide is not exceptional. 
(2) About half of this error may be due to the inadequate treatment of 
shallow-water effects. 
(3) The remaining half of the error is due to tidal constituents which are 
not included in the schedules given by Sir G. H. Darwin in 1883, and whose 
origin is not definitely known. 
(The constituents scheduled by Sir G. H. Darwin will be spoken of as 
‘1883’ or ‘ Darwinian’ constituents.) 
(4) While the methods of analysis and prediction are restricted as hitherto 
to the consideration of the ‘1883’ constituents only there can be no material 
improvements in either analysis or prediction. This is a direct consequence 
of (3). 
(5) Time devoted to the modification of harmonic ‘ constants’ by repeated 
analyses would probably be better spent in analysing for new constituents. 
These conclusions are based upon the work of which an account is now 
given. The Report is divided into three parts :— 
I. A general account of procedure and results. 
II. A statement of methods. (Some of these may be of interest to those 
not concerned with tidal applications—e.g. the methods of calculation 
and summation of harmonic terms.) 
IIT. A report on the behaviour of predicting machines. 
The subjects of reference have not been fully investigated; the long-period 
tides and meteorological effects have yet to be considered, and the residues 
mentioned in (3) above need thorough examination. The Committee, therefore, 
asks to be reappointed. 
PART I. 
General Account of Procedure and Results. 
§ 2. Some indirect evidence as to the errors of analysis and prediction is 
furnished by a comparison of observations and predictions such as is contained 
in the ‘ Report on the Harmonic Prediction of Tides’ by the Secretary in 1920. 
But such evidence is not sufficient to indicate the causes of the discrepancies, 
and the only satisfactory course at the outset seemed to be that of the continuous 
subtraction of such partial tides as could be determined, together with examina- 
tions of the successive residues. Obvious tidal constituents, or such constituents 
as were indicated in the standard schedules (or otherwise), were to be removed 
and the residues successively treated until there would be nothing left save 
weather effects and other non-periodic perturbations of mean sea-level. 
Success depended upon the accuracy of the observations to be treated, and 
oF the accuracy of calculations. Concerning the former it was concluded 
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