192 
MR. LLOYD ON THE DIFFERENCE OF LEVEL BETWEEN 
Brass standard in the dock-yard on the eastern 1 
point of mast slip J 
A 4^ in small north-east gateway of Greenwich \ 
College, from the main road J 
Small brass standard underneath the transit at 1 
Greenwich Observatory J 
Little brass standard on the plinth of the statue of) 
George II. in Greenwich Hospital j 
n on one of the iron plates near the south side of) 
the lock of the City Canal J 
Brass standard at the West India Docks . . . . 
Brass standard at Regent’s Canal 
A n on the top of a granite post close outside the") 
entrance from Ratcliffe Highway to the London )> 
Docks J 
On the top of a gun in the Docks near the bridge 1 
of the eastern basin J 
Brass standard St. Catherine’s Docks 
Brass standard near the Traitor’s Arch in the Tower 
Brass standard at landing-place of New London 
Bridge 
} 
above 
Feet. 
1.6545 
ditto 
9.9975 
ditto 
140.6897 
ditto 
5.1157 
ditto 
1.9008 
ditto 
1.3018 
ditto 
2.4418 
ditto 
16.0915 
ditto 
13.1646 
ditto 
4.3143 
ditto 
1.2854 
below 2.3967 
As it may be expected that I should state the manner in which I made the 
preceding observations, in order that a judgement may be formed of the con- 
lidence to be placed in them, I shall give a concise description of the field 
operations, and of the calculations necessary to complete the observations, and 
place them as they are in the book *. 
After examining the ground, the particular line for carrying on the levellings 
was selected and marked out, when pickets were driven in at proper distances, 
according to the range of the instrument over the ground. 
In the first part of the work the levelling was carried on as follows, the in- 
urnment being perfectly adjusted, and the station staves placed on their re- 
spective pickets. I made four observations, the telescope being in a different 
* The field-book and all the other papers connected with the preceding operations are preserved at 
the Royal Society’s Apartments. 
