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TIDAL OBSERVATIONS. 4.95 
any trustworthy tide-gauge; and, through his kind assistance, I accordingly 
received from Staff-Commander Burdwood, R.N., those of the Royal Harbour 
of Ramsgate for 1864. From the beginning of last winter till the present 
time I have been engaged in the reduction of these observations, chiefly 
assisted by Mr. Ebenezer Maclean, but also by Mr. James Smith and Mr. 
William Ross, students of the Natural-Philosophy Class of Glasgow Uni- 
versity, last Session, who volunteered to perform the laborious processes of 
measurement and calculation required. The heights above a certain point 
near the bottom of the scale, chosen to avoid negative quantities, were mea- 
sured from the diagrams for noon and midnight 6 p.m. and 4.M.,3 P.M. and A.M., 
9 a.m. and p.m.; but after some preliminary calculations had shown what 
valuable results might be expected, the measurement was made for every 
mean solar hour of the year, and the numbers written down in a book, with 
a page 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 semiannual 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 according to the harmonic 
plan, I felt justified in bringing the subject before the British Association 
and proposing that the cooperation 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 investigation proposed. Acting on the 
advice of the Astronomer Royal, I have put the work of continuing the com- 
putations for the Ramsgate observations into the hands of a skilled calculator, 
Mr. KE. 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 little time as possible in communicating the results to the 
Committee. I shall keep in view the trial (with which I commenced work 
on these observations) to find how much of valuable results can be obtained 
from a comparatively small number of observations, for instance, observations 
every three hours of the twenty-four, instead of every hour, or every three 
hours of the day half of the twenty-four, for the purpose of learning how 
to reduce, as far us possible, the labour and inconvenience imposed upon those 
to whom may be committed the execution of observations taken in future 
according to advice from this Committee. 
11. Probably the best personal observations that have ever been made on 
the tides are those described by Captain Sir James Clark Ross, R.N., in the 
Philosophical Transactions for June 1854, as having been made by the 
officers and petty officers of H.M. ships ‘ Enterprise’ and ‘ Investigator,’ 
every hour of the twenty-four, for nine months, commencing November Ist, 
1848,in Port Leopold. A full harmonic reduction of these observations, and 
of the simultaneously observed heights of the barometer, must, as early as 
possible, be executed by this Committee. 
12. A beautiful synthesis of the complex dynamical action to which the 
tides are due, imagined by Laplace, will be used in this Report to enable us 
to avoid circumlocution, A number of fictitious stars (“astres fictifs”) are 
assumed to move, each uniformly in the plane of the earth’s equator, with 
