118
SOME ESSEX BOULDERS.
with a peculiar glazed appearance when broken, not like the
fractured surface of quartzite, but with more of the appearance
of a thin covering of calcite. A much larger block of this same kind
of sandstone is lying in the farmyard at Pond Park, about two miles
to the south-east of Felstead, and from this I have obtained several
fragments of Pecten orbicularis; they were kindly examined for me
by Mr. H. Keeping, Curator of the Woodwardian Museum at Cam-
bridge, and he wrote me word to say that they were most probably from
the Lower Greensand, corresponding to a bed in fig. 1 in his paper on
the Lincolnshire Neocomian*. It would be an interesting question
whether these blocks can possibly have come from the Lincolnshire
beds. But the boulders of limestone are really of greater interest than
the sandstone, as there are in them fossils in abundance, so that one can
identify them with much greater certainty. Of these a considerable
number are of a dark grey crystalline texture, one of them measur-
ing as much as three feet by two feet six inches by two feet,
and another two feet three inches by two feet by one foot three
inches. They weather a light bluish grey, and are very hard. I
have made some eighteen or twenty microscopic sections of these,
and amid pieces of broken shell and stems of encrinites they contain
some beautifully perfect specimens of the foraminifera, which are
described and figured in Mr. Brady's well-known monograph of the
Permian and Carboniferous Foraminifera. As a rule these crystalline
blocks are of fine texture and abound in specimens of Valvulina,
Endothyra, and Trochammina.
In addition to these hard crystalline blocks, there are others of a
much looser texture. In the "Swan Inn" yard at Felstead there is a
large boulder of soft limestone, measuring three feet by two feet six
inches by two feet, which is very much weathered, the rain and frost
having deeply wrinkled the sides: this is a glauconitic limestone,
and doubtless belongs to the Greensand beds. But perhaps the most
common are the boulders of Jurassic limestone, chiefly belonging to
the Oxford and Kimmeridge Clay series. Of these, two very large
boulders might have been seen a short time ago in the high banks of
the railway cutting at Dunmow; they were slicking out at the bottom
of the Chalky-boulder Clay, which covers the top of the cutting,
extending down the surface some five or six feet in depth. Under-
neath this, just at its junction with some few inches of laminated
*"Quarterly Journal Geological Society," May, 1882, "On Some Sections of Lincolnshire
Neocomian." H. Keeping.