FALL OF THE TIDE IN THE RIVER THAMES. 
3 
I may remark that the results from the various tides would have agreed more ex- 
actly if an observed time of Deptford high water had been used (in the conversion of 
time into phase) instead of predicted time of London high water: but the process 
would have been more troublesome, and the advantage very small. 
As there was evidently a variation in the law depending on the range of the tide, 
the observations were next divided into two nearly equal groups ; one (of fifteen com- 
plete tides) comprising those in which the range was small ; the other (of sixteen 
tides) comprising those in which the range was large. The former is called division 
A, and the latter division B. These two divisions were treated separately ; although 
the methods of treating them are in every respect the same. 
The next step was (in each division) to pick out all the phases included between 
0° and 10°, and their corresponding converted depressions ; and to take the mean of 
each of these series of numbers : then to pick out all the phases included between 
10° and 20°, and their corresponding converted depressions; and to take the mean 
of each of these series of numbers : and so on. In this manner there were obtained, 
in each division, two columns of numbers (every one of which was the mean of about 
twenty-two numbers) ; one of them being a series of phases very near to 5°, 15°, &c., 
and the other being the corresponding converted depression. As there was no diffi- 
culty in inferring from these numbers, with considerable accuracy, the change of con- 
verted depression corresponding to a very small change of phase, it was easy to apply 
the correction required to adapt the converted depressions to the exact values of 
phase 5°, 15°, 25°, &c. In this manner the two following Tables were formed. 
Division A. 
Mean depression of high water 5 ft. 11 in. 
Mean range of tide 15 ft. 3 in. 
Phase. 
Converted 
depression. 
Phase. 
Converted 
depression. 
O 
5 
0-068 
185 
1-980 : 
15 
0-167 
195 
1-955 
25 
0-318 
205 
1-845 
35 
0-476 
215 
1-731 
45 
0-626 
225 
1-581 
55 
0-783 
235 
1-413 
65 
0-921 
245 
1-266 
75 
1-062 
255 
1-075 
85 
1-183 
265 
0-921 
95 
1-299 
275 
0-760 
105 
1-438 
285 
0-612 
115 
1-525 
295 
0-468 
125 
1-645 
305 
0-347 
135 
1-725 
315 
0-236 
145 
1-810 
325 
0-135 
155 
1-885 
335 
0-057 
165 
1-934 
345 
0-021 
175 
1-965 
355 
0-016 
Division B. 
Mean depression of high water 3 ft. 6 in. 
Mean range of tide 19 ft. 2 in. 
Phase. 
Converted 
depression. 
Phase. 
Converted 
depression. 
O 
5 
0-030 
185 
1-912 
15 
0-118 
195 
1-960 
25 
0-249 
205 
1-981 
35 
0-406 
215 
1-923 
45 
0-563 
225 
1-753 
55 
0-697 
235 
1-568 
65 
0-830 
245 
1-366 
75 
0-942 
255 
1-156 
85 
1-057 
265 
0-988 
95 
M7l 
275 
0-830 
105 
1-272 
285 
0-683 
115 
1-371 
295 
0-557 
125 
1-469 
305 
0-454 
135 
1-558 
315 
0-347 
145 
1-645 
325 
0-232 
155 
1-725 
335 
0-116 
165 
1-794 
345 
0-042 
175 
1-851 
355 
0-008 
b 2 
