572 : REPORT—1904. 
Quartz-porphyries are common, and many probably belong to this family. 
Porphyritic intermediate and basic lavas from the Cheviots and Central 
Scotland are very common, and several specimens are of the Garlton plateau 
family. 
A very characteristic quartz-porphyry is recognised by Professor Sjégren as 
from Dalecarlia. 
Many porphyrites and andesites and a very fine Limburgite have not yet been 
identified. 
7. On Tidal Action in the Mersey in Recent Years. 
Ly James N. Suoonsren, B.A., MInst.C.E. 
It is well known that during the past ten years a very considerable improvement 
has taken place in the sea approaches to Liverpool, in Liverpool Bay and in the 
lower parts of the river Mersey, by the removal of 16 feet or more in depth of 
the sandy bar which obstructs the seaward entrance to Liverpool Bay, and by the 
dredging of certain shoals in the Queen's Channel leading up to Liverpool itself. 
In carrying out these operations 80 million tons of sand have been dredged during 
the ten years which have passed, with the result that a minimum depth of 
27 feet at the low water of equinoctial spring tides has been secured for the navi- 
gation over the bar, and throughout the entire distance up to the Liverpool 
Landing Stage. The question has been repeatedly raised as to whether the above 
increased deepening of the approach channels, together with the smoother channel 
in the river itself, due to the extension of the dock walls, had led to any altera- 
tion in the flow of the tidal current or in the range of the tides themselves. 
The Committee of the Association appointed, at the instance of Section G, at 
the meeting last year at Southport, after a careful examination and comparison 
of tidal records extending over a period of nearly forty years, have reported that 
after an investigation, both by harmonic analysis and by direct comparison of the 
tidal curves themselves, no material change, practically, has taken place in the 
tidal régime of the Mersey. Small local alterations, it should be added, in sand- 
banks and shoals, and due largely to particular current variations, keep going on, 
as they have been doing for the last eighty years or more—of which we have 
records. But these alterations can generally be controlled by carefully guarding 
against any diminution in the tidal scour of the ebb tide, a duty which is 
entrusted to the Mersey Conservators, who are specially appointed for that 
purpose. 
8. Note on certain High-level or Plateau Gravels on the North Side of the 
Lamisian Area, and their Connection with the Tertiary History of 
Central England. By A. Irvine, D.Sc. B.A. 
The author records some results of his observations of these gfavels during the 
last ten years, as supplementary to what he has written in papers which appeared _ 
from ten to twenty years ago on the high-level or plateau gravels south of the 
Thames,’ He has found these stratified gravels on the north side of the Thames 
to be strictly comparable in their s¢rwctwre, and in their relation to the Eocene 
formations on which they lie, with those which cap the hills of Berks and Surrey, 
these hills representing the approximate levels of the ancient plateau out of which 
the upland valleys and terraces of the Thames area on both sides have been 
carved by subsequent denudation. The gravels dealt with in this note especially 
are found in the district of Bishop’s Stortford and Stansted, on the high ground 
bordering the counties of Herts and Essex. They have been omitted by the late 
Sir Joseph Prestwich in his discussion of the Mundesley and Westleton beds in his 
three papers given to the Geological Society in 1890. 
The composition of these stratified gravels is described, and it is pointed out 
' See Proc. Geol. Association, vol. viii. 1893; Q.7.G.S., vol. xlvi. 1890; Science 
Gossip, May and June, 1891; and Geol. Mag., May 1893, ° 
