TRANSACTIONS OF THE SECTIONS. 87 
the back-water, diminish the scouring of the reflux tide, or, by alter- 
ing the form of the river-shores, tend to throw the current into new 
directions, and to stop up the existing channels; Captain Denham 
strongly urged the propriety of a power, vested in local guardians, 
to interfere whenever attempts should be made to encroach by em- 
bankments, or in any other way, on the present high-water-marks, as, 
in the present state of the law, a vital injury might be done to the port 
before an injunction could be obtained to restrain such dangerous 
operations. Captain Denham then explained and exhibited the simple 
gauge by which he had drawn up the water from various depths, to 
test the quantity of earthy matter suspended in it, and thus to mea- 
sure at once simply and effectually, the aggregate quantity silently and 
almost imperceptibly circulating with the waters of this great estuary, 
and to deduce, with certainty, the practical as well as geological re- 
sults of a continuance of the action of such natural causes under their 
present circumstances, and of the probable effect of any artificial 
modification of them. This instrument is a cylinder, seventeen inches 
long, and four in diameter, having a valve at each end, the lower 
Opening inwards, the upper outwards; so that on descending, both 
valves would be opened by the pressure of the water, which would 
flow freely through the cylinder, and, on ascending, both valves would 
be closed, and the water which had entered at the lowest point of its 
descent, retained within it. The samples of water were taken up at half- 
hour intervals during the whole of the flood and ebb, and at depths in 
each series from six feet to thirty. The waters were more turbid at 
two hours’ flood, and at two, three, four hours’ ebb, and the water at 
thirty feet depth contained 4, more of silt than at other depths. 
Thirty feet being the height of the spring-tide column, that was the 
maximum depth gauged. 
On the Changes which have taken place in the Levels of Scotland. 
By Mr. J. Smitu. 
Mr. Smith stated that there was abundance of evidence that changes 
had taken place in the relative levels of land and sea in Great Britain, 
as well as elsewhere. The phenomena, however, proving this fact had 
been involved in confusion under the title of diluvium; but he had full 
reason, from a careful examination of the fossils, to decide that much of 
these deposits belonged to the tertiary series, and not to the more recent 
deposits called diluvium. He had traced them in the county of Ayr, 
and indeed all round Scotland, the general height being 40 feet, though 
Mr. Gilbertson had stated an instance in which such a deposit had 
been found at 300 feet; from its generality, however, he considered 
40 feet to have been the height of a distinct ridge or deposit. Finely 
_ laminated clay is a principal member of this deposit, and from the pro- 
portion of extinct and recent species, in the whole 113 species of shells, 
which he had discovered, he considered the deposit to agree with the 
Newer Pleiocene of Messrs. Lyell and Deshayes. 
