220 
MR. LUBBOCK ON THE TIDES. 
ascertained that at Brest the height of high water varies inversely as the height of 
the barometer, and that the ocean rises ‘223 metre, or 878 inches, for a depression 
of '0158 metre, or *622 inch, in the barometer *. 
In order to confirm this interesting result, and to ascertain the variation in the height 
of high water at Liverpool simultaneous with the variation of the atmospheric pres- 
sure, I requested Mr. Dessiou to calculate from our tables the heights and times of 
high water at Liverpool for the year 1784, and to compare the errors of the calculated 
heights and times with the heights of the barometer as recorded by Mr. Hutchinson 
for that year. The errors were divided into three categories : 
inches. inches. 
Those for a height of barometer between 29 and 29*50 
29*50 and 30 
30 and 30*50 
inches. 
inches. 
For 29*25, mean of 148 
29*76, 328 ' 
30*16, 232, 
results, we found the mean f— 5*6 
error in the calculated^ -f- *1 
heights of high water . . . 1+4*5 
Hence we may say roughly that at Liverpool a fall of one tenth of an inch in the 
barometer raises the tide an inch, cceteris paribus. The time of high water appeared 
not to be much affected. 
The same errors in the calculated times and heights for 1784 were again classed, in 
order if possible to ascertain the effect of the wind, and the following results were 
obtained. 
Error in calcu- 
lated Time of 
High Water. 
Error in calcu- 
lated Height of 
High Water. 
Height of 
Barometer. 
1 
Number of 
Observations. 
N. 
m 
+ *i 
inches. 
+ 1-4 
29*80 
32 
N.N.E. 
— -8 
+ 8-9 
29*83 
19 
N.E. 
— -8 
+ 9*7 
29*79 
28 
E.N.E. 
+ 1*7 
+ 9*1 
29*77 
16 
E. 
— -8 
+ 5*2 
29-86 
38 
E.S.E. 
-2-8 
+ *7 
29-76 
21 
S.E. 
-1-6 
+ 1-0 
29-91 
141 
S.S.E. 
— 4-2 
+ 2-2 
29-80 
37 
S. 
-5-0 
-4*7 
29-60 
4 
S.S.W. 
-3-2 
— 4-2 
29-25 
12 
S.W. 
-1*7 
-3-0 
29-57 
45 
W.S.W. 
-4-2 
-5*5 
29-54 
42 
w. 
-1-6 
— -4 
29-73 
87 
W.N.W. 
-2-9 
+ 1*2 
29-89 
28 
N.W. 
— 1-5 
— -3 
29-38 
72 
N.N.W. 
-3-9 

29-61 
04 
Hence it appears that north-easterly winds at Liverpool depress the tide, and south- 
* See Connaissancc des Temps, 1834. 
