Harmonic Analysis of Tidal Observations. 



139 



Kathiwadar) the epoch is Oh. of (old) astronomical time, or civil 

 noon, of the day specified. 



In Table I is given the latitude and longitude of the several ports. 



In Table II the values are given of H and k for each year or period 

 analysed for the ports specified at the head; these are the values 

 deduced from the results of 1872, 1876, 1878, and from those of the 

 Indian Survey. 



The initial of the tide is shown in the margin. 



The last column for each port gives the mean of the values for the 

 years under observation. An inspection of the numbers from which 

 the mean is derived shows the degree of consistency between the num- 

 bers obtained in the several years. The number of results is hardly 

 sufficient to make it worth while to deduce a probable error for H 

 and k ; moreover, it would be a somewhat arduous task to do so. 



Table III is a summary of Table II, giving only the mean values, 

 together with the number of years from which the mean is derived, 

 and this is of much value for the theoretical discussion of the tides. 



Table IV gives Mr. Ferrel's results from the Reports to the United 

 States Coast Survey. 



The tables give altogether results for 43 ports, and for 137 periods 

 of observation and analysis. 



# [We have to thank Mr. Edward Roberts, the importance of whose 

 work in this subject is well known, for having reduced the results 

 given in the paper of 1878, viz., those for Freemantle, Mauritius, E. 

 Falkland, Malta, Marseilles, and Toulon. In several of these the 

 heights were stated in centimetres, but they are now reduced to feet 

 and decimals. 



Professor Ferrel has carried out an harmonic analysis at several 

 ports for the United States Coast Survey. The process adopted by 

 him does not appear to be identical with the method of the British 

 Association, and there seemed to be room for doubt as to whether the 

 results were truly comparable with ours. In answer to an inquiry on 

 this point, addressed to the United States Coast Survey, Mr. Ferrel 

 kindly sent a memorandum to the Superintendent, Mr. Hilgard, 

 which has been forwarded for our information. The memorandum, 

 dated Washington, April 27th, 1885, runs as follows : — 



"The results of harmonic analyses of tide observations of the 

 United States Coast and Geodetic Survey are found in Report of the 

 British Association for 1872, and the Reports of the Coast and 

 Geodetic Survey of 1878, App. No. 11; 1882, App. No. 17; 1883, 

 App. No. 9. The results for Governor's Island have not yet been 

 printed. 



* This paragraph and the corresponding portion of the tables were added on 

 May 15, 1885, subsequently to the presentation of the paper. These results of 

 1878 are only given in Table III, and not also in Table II. 



