Discourses: Biological and Geological Essays | Page 3

may vary almost indefinitely. If the famous paint- root of
Florida, which kills white pigs but not black ones, were abundant and
certain in its action, black pigs might be substituted for white in the
course of two or three years. If, on the other hand, it was rare and
uncertain in action, the white pigs might linger on for centuries.
T.H. HUXLEY.
HODESLEA, EASTBOURNE,
April, 1894.

CONTENTS
I
ON A PIECE OF CHALK [1868] (A Lecture delivered to the working
men of Norwich during the meeting of the British Association.)
II
THE PROBLEMS OF THE DEEP SEA [1878]
III
ON SOME OF THE RESULTS OF THE EXPEDITION OF H.M.S.
"CHALLENGER" [1875]
IV
YEAST [1871]
V
ON THE FORMATION OF COAL [1870] (A Lecture delivered at the
Philosophical Institute, Bradford.)
VI

ON THE BORDER TERRITORY BETWEEN THE ANIMAL AND
THE VEGETABLE KINGDOMS [1876] (A Friday evening Lecture
delivered at the Royal Institution.)
VII
A LOBSTER; OR, THE STUDY OF ZOOLOGY [1861] (A Lecture
delivered at the South Kensington Museum.)
VIII
BIOGENESIS AND ABIOGENESIS [1870] (The Presidential Address
to the Meeting of the British Association for the Advancement of
Science at Liverpool.)
IX
GEOLOGICAL CONTEMPORANEITY AND PERSISTENT TYPES
OF LIFE [1862] (Address to the Geological Society on behalf of the
President by one of the Secretaries.)
X
GEOLOGICAL REFORM [1869] (Presidential Address to the
Geological Society.)
XI
PALAEONTOLOGY AND THE DOCTRINE OF EVOLUTION
[1870] (Presidential Address to the Geological Society.)

I
ON A PIECE OF CHALK
[1868]
If a well were sunk at our feet in the midst of the city of Norwich, the

diggers would very soon find themselves at work in that white
substance almost too soft to be called rock, with which we are all
familiar as "chalk."
Not only here, but over the whole county of Norfolk, the well-sinker
might carry his shaft down many hundred feet without coming to the
end of the chalk; and, on the sea-coast, where the waves have pared
away the face of the land which breasts them, the scarped faces of the
high cliffs are often wholly formed of the same material. Northward,
the chalk may be followed as far as Yorkshire; on the south coast it
appears abruptly in the picturesque western bays of Dorset, and breaks
into the Needles of the Isle of Wight; while on the shores of Kent it
supplies that long line of white cliffs to which England owes her name
of Albion.
Were the thin soil which covers it all washed away, a curved band of
white chalk, here broader, and there narrower, might be followed
diagonally across England from Lulworth in Dorset, to Flamborough
Head in Yorkshire--a distance of over 280 miles as the crow flies. From
this band to the North Sea, on the east, and the Channel, on the south,
the chalk is largely hidden by other deposits; but, except in the Weald
of Kent and Sussex, it enters into the very foundation of all the
south-eastern counties.
Attaining, as it does in some places, a thickness of more than a
thousand feet, the English chalk must be admitted to be a mass of
considerable magnitude. Nevertheless, it covers but an insignificant
portion of the whole area occupied by the chalk formation of the globe,
much of which has the same general characters as ours, and is found in
detached patches, some less, and others more extensive, than the
English. Chalk occurs in north-west Ireland; it stretches over a large
part of France,-- the chalk which underlies Paris being, in fact, a
continuation of that of the London basin; it runs through Denmark and
Central Europe, and extends southward to North Africa; while eastward,
it appears in the Crimea and in Syria, and may be traced as far as the
shores of the Sea of Aral, in Central Asia. If all the points at which true
chalk occurs were circumscribed, they would lie within an irregular

oval about 3,000 miles in long diameter--the area of which would be as
great as that of Europe, and would many times exceed that of the
largest existing inland sea--the Mediterranean.
Thus the chalk is no unimportant element in the masonry of the earth's
crust, and it impresses a peculiar stamp, varying with the conditions to
which it is exposed, on the scenery of the districts in which it occurs.
The undulating downs and rounded coombs, covered with
sweet-grassed turf, of our inland chalk country, have a peacefully
domestic and mutton- suggesting prettiness, but can hardly be called
either grand or beautiful. But on our southern coasts, the wall-sided
cliffs, many hundred feet high, with vast needles and pinnacles
standing out in the sea, sharp and solitary enough to serve as perches
for the wary cormorant, confer a wonderful beauty and grandeur upon
the chalk headlands. And,