308 Proceedings of Philosophical Societies. [Aprit, 
openéd, for the purpose of drawing the charge, at which period 
the coke presents the appearance of a glowing pavement, rifted 
into perpendicular columnar masses, the bases of which rest on the 
floor of the oven. Adherent to the sides of these rifts are occa- 
sionally found concretions, of a rather flat and small botryoidal 
external figure, of an iron black colour, and highly metallic lustre, 
resembling grey manganese, or black hematitic iron ore. 
Intermixed with these are small arborescent tufts, about a quarter 
of an inch in length, adherent by their base to the mass of coke ; 
each branch of which, when examined by the microscope, appears 
composed of minu'e botryoidal shoots. 
A description of certain beds occurring above the chalk, espe- 
cially of the plastic clay, by the Rev. William Buckland, M.G.S., 
was read. é' 
The paper begins with a description of the beds, which occur at 
and about Reading, as exposed by various quarries. ‘The lowest 
bed is the flinty chalk, immediately upon which rests a bed of sand, 
about eight feet in thickness; the lower part of which abounds in 
green particles, in rolled and angalar flint pebbles, in small round 
teeth of fish, and in a species of oyster, commonly called the Reading 
eyster ; the upper part of the bed contains a few green particles, but 
no rolled pebbles or organic remains. Immediately upon this bed 
~ yests a bed three feet thick of fuller’s earth; above which occurs 
the plastic clay, in fine beds, more or less mixed with sand, for 
the most part of a dark red colour, and above 35 feet in thickness : 
these clays contain ne organic remains or septaria. The next and 
highest stratum in the series is a loam 11 feet thick, becoming 
more clayey towards the bottom, and then containing ochreous 
concretions and balls of pyrites. 
These beds occupy much of the ground between Reading and 
Newbury, and appear to lie between the chalk and the London 
clay; corresponding, therefore, in position, with the plastic clay 
of the Isle of Wight, and of Dorsetshire, as described by Mr. 
Webster; and with the plastic clay of the basin of Paris, which, 
according to MM. Cuvier and Brongniart, lies between the 
chalk and the calcaire grossier. 
The green sand of Reading appears in many places. near Lon- 
don, and south of the Thames, resting immediately upon the 
chalk, as at Woolwich, Lewisham, Charlton, &c.; but containing 
no organic remains. 
Mr. Webster, in his valuable paper, “ On the Formations above 
the Chalk,” hesitates in what part of the series to place the shell 
beds of Woolwich; the determination of which question forms one 
of the important points in the present paper; and from many con- 
siderations, founded on personal inspection, and an authenticated 
list of strata, Mr. B. is inclined to consider them as occupying the 
middle part of the plastic clay formation, a formation which con- 
stitutes a real and important number of the great series, although 
