222 POPULAR LECTURES AND ADDRESSES. 



for each day. Certain averagings of these results, 

 arranged in proper groups, were then made, and 

 somewhat closely approximate determinations of 

 the amplitude and epoch of the solar semidiurnal 

 and lunar semidiurnal tides were deduced. I 

 also found very decided indications of an annual 

 rise and fall, which seemed to exceed the amount 

 of the solar semidiurnal tide, and to make the 

 mean level very sensibly higher in autumn than in 

 spring, an effect probably to be accounted for by 

 an annual period in the amount of water received 

 into the sea by drainage and the melting of ice, 

 and from the direct fall of rain into it. With 

 these indications of what might be expected from 

 a thorough reduction of tidal observations accord- 

 ing to the harmonic plan, I felt justified in bring- 

 ing the subject before the British Association and 

 proposing that the co-operation of a Committee 

 should be invited, and a grant of money made to 

 defray expenses which might be found necessary 

 for carrying on the several parts of the investiga- 

 tion proposed. Acting on the advice of the 

 Astronomer-Royal, I have put the work of con- 

 tinuing the computations for the Ramsgate ob- 

 servations into the hands of a skilled calculator, 

 Mr. E. Roberts, recommended to me by Mr. Farley 

 of the Nautical Almanac Office, for this purpose. 

 With his very able assistance I hope soon to have 

 the harmonic analysis completed for the year's 

 observations now in his hands ; and I shall lose as 



