290 E. A. Martin—Brighton Chff Formation. 
The above is extracted from a private letter of my brother’s, written 
September 15, 1909, in answer to some questions I had asked relating 
to the behaviour of rivers. It seems to me likely to interest others 
besides myself, and he has given me leave to make any use of it. 
I have printed it as written. 
The figures work out as follows :— 
The maximum quantity of silt observed in suspension gives a trifle 
less than 1 cubic foot of clay from 300 cubic feet of water. 
The discharge of water in the four above-named months is 4,216,320 
millions of cubic feet. 
If this contained the observed maximum of silt it would be sufficient 
to deposit a layer of 1 foot of clay over 503 square miles. 
II.—Some OxssEervations on THE Bricguton Crirr Formarron.! 
By Epwarp A. Martin, F.G.S. 
URING the past eighteen years I have made certain observations 
on the cliff formation on the east of Brighton and on the sections 
successively brought into view by repeated falls of the cliff. The 
chief item to be noted from -them is, that as the cliff wears back, the 
base-platform of chalk grows in height, that is, the old surface of 
the chalk dips towards the south. Also, that the layer of sand which 
Prestwich found above the chalk grew thinner and thinner, until it 
has now completely disappeared. At the same time the raised beach 
has grown in thickness from 13 feet to 12 feet. 
In 1890 the raised beach still remained about a foot and a half 
thick, as noted by Prestwich, with about 6 feet of sand beneath it. 
An illustration of the cliffs at this date has appeared in a little work 
called Amzdst Nature's Realms, and can be referred to there. An old 
groyne remained, but it was in a very damaged condition, and it was 
noticeable that the usual accumulation of beach on the western side 
had not taken place there. The groyne was subsequently removed, 
and a low concrete wall was constructed almost as far eastward as 
where the wooden groyne formerly stood. When visiting the formation 
in 1892 I noted that there was still about 14 feet of the raised beach, 
but between 8 and 4 feet of sand beneath it, the thickness between 
these limits constantly varying along the face of the cliff, thus showing 
a considerable reduction in two years. 
During a visit to Brighton in September, 1895, the changes which 
had taken place were very noticeable, owing to the rapid undermining 
of the cliff formation, and the action of the weather on the porous 
materials of which it is composed. For many years the eastern limit 
of the beds had been obscured to a more or less extent, but owing to 
the great falls that had taken place it was possible to place a limit 
upon the eastern extension of the beds. This was at a point at about 
300 yards east of the Abergavenny Inn. At this point there was 
a distinct slope upwards of the lines of bedding, these being always 
more or less obscure, but here sufficiently clear to mark the shore of 
1 Paper read before the Geological Society, an abstract of which appeared in the 
Quart. Journ. Geol. Soc., May, 1909. 
