'to Mr Robison on the Difference of Level 
Again^ in the Number for November 1816, p. 692* “ The 
‘‘ difference between the height of the sea on the east and west 
coasts of Britain is 50 feet.” 
In the Number for March 1817, p. 177. Mr Galton, F. R. S. 
in a paper on canal levels, says, in connecting these sections, 
I observed with some surprise, that the Thames at Brentford 
appeared to be fourteen feet lower than the junction of the 
“ Duke of Bridge wateFs canal with the Mersey at Runcorn.” 
The discrepancy of these statements, — the obvious impossibi- 
lity of the one, and the improbability of the other, made me 
desirous of ascertaining the point of fact, where the two seas 
approach so nearly as in the Friths of Forth and Clyde. For 
this purpose, I instructed the superintendants of the east and 
west districts of t}ie Forth and Clyde Canal, (on three particu- 
lar days), to take notes of the rise and fall of the tides at their 
respective ends. . I at the same time took measures for ascer- 
taining the actual difference of level of every lock, when full 
and when empty. I take the liberty of sending you the results, 
in the hope that some of your readers, who may possess infor- 
mation regarding the slope of the surfaces of the two friths, may 
communicate what may be necessary to complete the connection 
of level to the open ocean on either side. When the Caledonian 
Canal shall have been completed, it would be satisfactory to 
have a similar set of levels from the Linnhe Loch to the Beauly 
Frilly. 
Observations at Bowling Bay on the tHyde : 
1S21, Feet. In. Feet. In. 
:Oct. 13. A calm day, High Water, 152.1, Low Water, 159.8| below summit-level. 
Nov. 1. Strong breeze 1 
from W. i 
Nov. 3. Nearly calm,-^ 
■ Do. 
150, 
do. 
157.101 
do. 
with consider- r 
able flood in f 
the river, 
Do. 
153.101 
do. 
157.2i 
do. 
The Superintendant considers the tides of 1st and 3d No- 
vember to be irregular, and that of the 13th October to be a 
fair average one. 
