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ANNALS 
OF 
PHILOSOPHY. 
MARCH, 1817. 
ArrTIcLe I, 
On Canal Levels.. By Samuel Galton, Esq. F.R.S. 
{With Three Plates.] 
(To Dr. Thomson.) 
SIR, _ Birmingham, Dec. 31, 1816, 
IT occurred to me several years ago that the lockage of canals, 
and their plans and sections, would afford the means of ascertaining, 
with a considerable degree of comparative precision, the relative 
height or level of all the places immediately situated upon those 
canals which communicate with one another; and that, in conse- 
quence, a number of fixed points would be obtained, from which 
the relative level of any objects in the vicinity of those canals 
might be more conveniently measured. 
Being possessed of several plans and surveys of canals, and 
having access to a still superior collection made by the direction of 
a canal committee, of which Iam a member, I have made sections 
of most of the canals in the kingdom. 
In connecting these sections, I observed, with some surprise, 
that the Thames at Brentford appeared to be nearly 14 feet lower 
than the junction of the Duke of Bridgewater’s Canal with the 
Mersey, at Runcorn. Hence I concluded that there must be an 
error in the surveys, or that the levels of the German Ocean, and 
of the Irish Channel, are very ditferent. “In your Annals this fact 
is stated. Ishall, therefore, with great pleasure, send to you some 
of the plans and sections which I have taken. 
1. The first, which I inclose, is a synoptic view of the principal 
eanals in England, in reference to their length only. (PI. LXIL.) 
Vor, IX, N° III, M 
