o14 REPORT—1890. 
of the estuary, have been read and recorded once a day. Contour 
surveys have been made after the first 16,000 tides, and again after the 
first 32,000, and in the longer experiment further surveys have been 
made ; in all, fifty complete-surveys have been made, and forty-four plans, 
showing contours at vertical intervals corresponding to 6 feet on a 
30-foot tide, are given in this report. 
The general conditions of each experiment, together with the general 
results obtained, are given in Table I., pp. 532, 533, and a description of 
each experiment is given in § III. 
_ The importance of a better means of recording the tide curves was 
mentioned in last year’s report. Such means have been (see p. 522) 
obtained during this year, and automatic tide curves have been taken as 
nearly as practical at corresponding numbers of tides during the experi- 
ments, these curves being taken at several definite sections in each tank. 
Two series of these curves have been taken in the later experiments, one 
in which the paper is moved by a clock, the pencil being moved by a 
float; the other in which the paper is moved by the tide generator, by 
which means exactly similar motion for the paper is secured at all points 
of the estuary, so that differences in the phases of the tide at different 
parts of the estuary are brought out. These curves are shown on the plates. 
Mr. H. Bamford has continued to conduct the experiments, but on 
account of the very great amount of detailed work the entire time of a 
second assistant has been occupied. For this the services of Mr. 
J. Heathcott, B.Sc., were obtained from October to February, when 
Mr. Heathcott obtained an appointment in the office of the engineer to 
the L. & N. W. R. in Manchester. Mr. Greenshields then applied for 
and obtained the post, and has continued the work with great patience 
and zeal. 
§ Il.—Grnerat Resunts anp Conciusions. 
A, The Limits to Similarity in Rectangular Estuaries—In the experi- 
ments of last year it was found (1) that as regards 
1. Rate of action as measured by the number of tides run ; 
' 2. Manner of action; and 
3. The final condition of equilibrium 
with tides of 0-176 foot and periods of 50 and 35 seconds the results 
= constant; (2) that, 
as regards rate and manner of action, the results obtained with tides of 
0-094 foot and periods 23°7 seconds were similar to those with the tide 
of 0:176; but the experiment had not proceeded to the final condition of 
equilibrium. 
It was also found that with tides of ‘088 foot and periods 35-4 seconds 
the results obtained differed in a marked manner from the others as 
regards rate and manner of action, so much so as to render the attainment 
of a final state of equilibrium impracticable. 
These results seemed to indicate that for each rise of tide there exists 
some critical period such that for all smaller periods the results would 
be similar according to the simple hydrokinetic law, while for larger 
periods the results would be dissimilar in a greater or less degree to 
those obtained with periods smaller than the critical period. Whether 
or not the results obtained with periods greater than the critical periods 
were similar, according to the hydrokinetic law = 
T.-C 
ee 
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