188 
MR. LLOYD ON THE DIFFERENCE OF LEVEL BETWEEN 
Having no observations of low-water mark at the canal, I have not the 
means of ascertaining the difference at the two places. 
The next place where a comparison of the tides was made was at the London 
Docks, at No. 418 of the Levels (see page 27), being on an iron on the south- 
west pier of the main entrance close to the first lock. This iron was 3.7570 
above the northern standard, and 5.7682 above the index mark by the side of 
the gates xxml, which mark answers to the 18-feet Trinity 
~A~ 
Therefore 3.7570 + 4.0661 — 5.7682 = 2.0549 the height of xxm above 
springtide high-watermark at Sheerness. And 2.0549 + 1.855 (the difference 
between spring tide and mean tide high-water mark at Sheerness) = 3.9099, 
the height of xxm above mean high-water mark at Sheerness. 
And 2.0549 -f- 3.699 (difference between spring and neap tides at Sheer- 
ness), = 5.7539, the height of xxm above neap tide at Sheerness. 
And 2.0549 -f- 9.085 (the difference between mean level and spring tide at 
Sheerness), = 11.1399, the height of xxm above the mean level of the sea at 
Sheerness. 
And 2.0549 + 17-615 (difference between spring high and low water at 
Sheerness), = 19.6699, the height of xxm above spring tide low-water mark at 
Sheerness. 
By the kindness of Mr. Lubbock I have received the following results of 
twenty-six years’ observations on the tides at the London Docks : 
January . 
Mean High Water, 
ft. in. 
. . . 21.275 . 
February . 
. . . 21.275 . 
March . . 
. . . 21.291 . 
April . . 
. . . 21.395 . 
May . . 
. . . 21.475 . 
.1 une . . 
. . . 21.395 . 
July . . 
. . . 21.291 . 
August 
. . . 21.250 . 
September 
. . . 21.291 . 
October . 
. . . 21.291 . 
November 
. . . 21.395 . 
December 
. . . 21.312 . 
Mean . . 21.333 
Spring High Water. 
Neap High Water. 
ft. in. 
ft. in. 
. 22.729 . 
. . 19.750 
. 23.002 . 
, . 19.145 
. 23.541 . 
. . 19.125 
. 22.854 . 
. . 19.375 
. 22.708 . 
. . 20.125 
. 22.50 
. . 20.250 
. 22.604 . 
. . 19.687 
. 22.708 . 
. . 19.562 
. 23.979 . 
. . 19.292 
. 22.937 • 
. . 19.229 
. 22.687 - 
. . 19.833 
. 22.458 . 
. . 19.870 
. 22.812 . 
. . 19.604 
