338 



REPORTS ON THE STATE OF BCIBNCB.— 1920. 



constituents of amplitudes less than O'l ft. The discrepancies over two typical day's 

 are shown in Fig. III. 



A Karachi record for 1868-71 was supplied by Mr. Parkes and analysed for all 

 the constituents considered at Liverpool, together with 



Q., J,. 



An hourly tide-table for 29 days in 1868 was made without To, Q,, J,, the long-period 

 constituents and MS4, but including several constituents of amplitudes less than 

 01 ft. The discrepancies over two typical days are shown in Fig. IV. 



FlQ. III. — Difference between Predictions and Record for Fort Point, 

 March 16 and 17, 1859. 



Fig, IV. — Difference between Predictions and Record for Karachi, 

 November 11 and 12, 1868. 



Next, three further yearly records of Liverpool tides were analysed for the same 

 constituents as before, with the exception of those of long period. 



Also, two further yearly records from Fort Point were analysed, the constituents 

 Q, and J, being added. 



A thirteeu months' record from Cat Island, in the Gulf of Mexico, was obtained 

 from the U.S. Survey, and analysed for the 



M, K, S, O, N, L, P, Q, J 



series, as well as the long-period constituents. 



From the Ramsgate 1864 record the constituents 2SM2 and SMS^were found, the 

 latter being a shallow-water constituent of speed iy — 6a + 2ri, derived from Sj 

 and Mg. 



Another yearly record from Karachi was analysed for all the constituents yet 

 considered. 



Four yearly records from Portland were analysed for the same constituents as at 

 Ramsgate, with the exception of those of long period. 



In the British Association Report for 1872, Roberts gave a harmonic development 

 of the semi-diurnal tide generating potential. 



15. In 1874 Lieut, (afterwards Col.) A. W. Baird, of the Survey of India, set up 

 tidal observatories at Hanstal, Navanar, and Oklia Point. He was afterwards 

 deputed to Europe to study the practical details of tidal registration and harmonic 

 analysis. With the help of Roberts in England, he analysed the records from the 

 observatories he had set up. 



The British Association Committee further analysed records for Hilbre Island, 



