Discourses - Thomas H. Huxley
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DISCOURSES:
BIOLOGICAL & GEOLOGICAL
ESSAYS
BY
THOMAS H. HUXLEY
1894
PREFACE
The contents of the present volume, with three exceptions, are either
popular lectures, or addresses delivered to scientific bodies with which
I have been officially connected. I am not sure which gave me the more
trouble. For I have not been one of those fortunate persons who are able
to regard a popular lecture as a mere _hors d'oeuvre_, unworthy of being
ranked among the serious efforts of a philosopher; and who keep their
fame as scientific hierophants unsullied by attempts--at least of the
successful sort--to be understanded of the people.
On the contrary, I found that the task of putting the truths learned in
the field, the laboratory and the museum, into language which, without
bating a jot of scientific accuracy shall be generally intelligible,
taxed such scientific and literary faculty as I possessed to the
uttermost; indeed my experience has furnished me with no better
corrective of the tendency to scholastic pedantry which besets all those
who are absorbed in pursuits remote from the common ways of men, and
become habituated to think and speak in the technical dialect of their
own little world, as if there were no other.
If the popular lecture thus, as I believe, finds one moiety of its
justification in the self-discipline of the lecturer, it surely finds the
other half in its effect on the auditory. For though various sadly
comical experiences of the results of my own efforts have led me to
entertain a very moderate estimate of the purely intellectual value of
lectures; though I venture to doubt if more than one in ten of an average
audience carries away an accurate notion of what the speaker has been
driving at; yet is that not equally true of the oratory of the hustings,
of the House of Commons, and even of the pulpit?
Yet the children of this world are wise in their generation; and both the
politician and the priest are justified by results. The living voice has
an influence over human action altogether independent of the intellectual
worth of that which it utters. Many years ago, I was a guest at a great
City dinner. A famous orator, endowed with a voice of rare flexibility
and power; a born actor, ranging with ease through every part, from
refined comedy to tragic unction, was called upon to reply to a toast.
The orator was a very busy man, a charming conversationalist and by no
means despised a good dinner; and, I imagine, rose without having given a
thought to what he was going to say. The rhythmic roll of sound was
admirable, the gestures perfect, the earnestness impressive; nothing was
lacking save sense and, occasionally, grammar. When the speaker sat down
the applause was terrific and one of my neighbours was especially
enthusiastic. So when he had quieted down, I asked him what the orator
had said. And he could not tell me.
That sagacious person John Wesley, is reported to have replied to some
one who questioned the propriety of his adaptation of sacred words to
extremely secular airs, that he did not see why the Devil should be left
in possession of all the best tunes. And I do not see why science should
not turn to account the peculiarities of human nature thus exploited by
other agencies: all the more because science, by the nature of its being,
cannot desire to stir the passions, or profit by the weaknesses, of human
nature. The most zealous of popular lecturers can aim at nothing more
than the awakening of a sympathy for abstract truth, in those who do not
really follow his arguments; and of a desire to know more and better in
the few who do.
At the same time it must be admitted that the popularization of science,
whether by lecture or essay, has its drawbacks. Success in this
department has its perils for those who succeed. The "people who fail"
take their revenge, as we have recently had occasion to observe, by
ignoring all the rest of a man's work and glibly labelling him a more
popularizer. If the falsehood were not too glaring, they would say the
same of Faraday and Helmholtz and Kelvin.
On the other hand, of the affliction caused by persons who think that
what they have picked up from popular exposition qualifies them for
discussing the great problems of science, it may be said, as the Radical
toast said of the power of the Crown in bygone days, that it "has
increased, is increasing, and ought to be diminished." The oddities of
"English as she is spoke" might be abundantly paralleled by those of
"Science as she is misunderstood" in the sermon, the novel, and the
leading article; and a collection of the grotesque travesties of
scientific conceptions, in the shape of essays on such trifles as "the
Nature of Life" and the "Origin of All Things," which reach me, from time
to time, might well be bound up with them.
The tenth essay in this volume unfortunately brought me, I will not say
into collision, but into a position of critical remonstrance with regard
to some charges of physical heterodoxy, brought by my distinguished
friend Lord Kelvin, against British Geology. As President of the
Geological Society of London at that time (1869), I thought I might
venture to plead that we were not such heretics as we seemed to be; and
that, even if we were, recantation would not affect the question of
evolution.
I am glad to see that Lord Kelvin has just reprinted his reply to my
plea,[1] and I refer the reader to it. I shall not presume to question
anything, that on such ripe consideration, Lord Kelvin has to say upon
the physical problems involved. But I may remark that no one can have
asserted more strongly than I have done, the necessity of looking to
physics and mathematics, for help in regard to the earliest history of
the globe. (See pp. 108 and 109 of this volume.)
[Footnote 1: _Popular Lectures and Addresses._ II. Macmillan and Co.
1894.]
And I take the opportunity of repeating the opinion, that, whether what
we call geological time has the lower limit assigned to it by Lord
Kelvin, or the higher assumed by other philosophers; whether the germs of
all living things have originated in the globe itself, or whether they
have been imported on, or in, meteorites from without, the problem of the
origin of those successive Faunae and Florae of the earth, the existence of
which is fully demonstrated by paleontology remains exactly where it was.
For I think it will be admitted, that the germs brought to us by
meteorites, if any, were not ova of elephants, nor of crocodiles; not
cocoa-nuts nor acorns; not even eggs of shell-fish and corals; but only
those of the lowest forms of animal and vegetable life. Therefore, since
it is proved that, from a very remote epoch of geological time, the earth
has been peopled by a continual succession of the higher forms of animals
and plants, these either must have been created, or they have arisen by
evolution. And in respect of certain groups of animals, the well-
established facts of paleontology leave no rational doubt that they arose
by the latter method.
In the second place, there are no data whatever, which justify the
biologist in assigning any, even approximately definite, period of time,
either long or short, to the evolution of one species from another by the
process of variation and selection. In the ninth of the following essays,
I have taken pains to prove that the change of animals has gone on at
very different rates in different groups of living beings; that some
types have persisted with little change from the paleozoic epoch till
now, while others have changed rapidly within the limits of an epoch. In
1862 (see below p. 303, 304) in 1863 (vol. II., p. 461) and again in 1864
(ibid., p. 89-91) I argued, not as a matter of speculation, but, from
paleontological facts, the bearing of which I believe, up to that time,
had not been shown, that any adequate hypothesis of the causes of
evolution must be consistent with progression, stationariness and
retrogression, of the same type at different epochs; of different types
in the same epoch; and that Darwin's hypothesis fulfilled these
conditions.
According to that hypothesis, two factors are at work, variation and
selection. Next to nothing is known of the causes of the former process;
nothing whatever of the time required for the production of a certain
amount of deviation from the existing type. And, as respects selection,
which operates by extinguishing all but a small minority of variations,
we have not the slightest means of estimating the rapidity with which it
does its work. All that we are justified in saying is that the rate at
which it takes place 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, in the East, chalk has its share in the formation of some
of the most venerable of mountain ranges, such as the Lebanon.
What is this wide-spread component of the surface of the earth? and
whence did it come?
You may think this no very hopeful inquiry. You may not unnaturally
suppose that the attempt to solve such problems as these can lead to no
result, save that of entangling the inquirer in vague speculations,
incapable of refutation and of verification. If such were really the
case, I should have selected some other subject than a "piece of chalk"
for my discourse. But, in truth, after much deliberation, I have been
unable to think of any topic which would so well enable me to lead you to
see how solid is the foundation upon which some of the most startling
conclusions of physical science rest.
A great chapter of the history of the world is written in the chalk. Few
passages in the history of man can be supported by such an overwhelming
mass of direct and indirect evidence as that which testifies to the truth
of the fragment of the history of the globe, which I hope to enable you
to read, with your own eyes, to-night. Let me add, that few chapters of
human history have a more profound significance for ourselves. I weigh my
words well when I assert, that the man who should know the true history
of the bit of chalk which every carpenter carries about in his breeches-
pocket, though ignorant of all other history, is likely, if he will think
his knowledge out to its ultimate results, to have a truer, and therefore
a better, conception of this wonderful universe, and of man's relation to
it, than the most learned student who is deep-read in the records of
humanity and ignorant of those of Nature.
The language of the chalk is not hard to learn, not nearly so hard as
Latin, if you only want to get at the broad features of the story it has
to tell; and I propose that we now set to work to spell that story out
together.
We all know that if we "burn" chalk the result is quicklime. Chalk, in
fact, is a compound of carbonic acid gas, and lime, and when you make it
very hot the carbonic acid flies away and the lime is left. By this
method of procedure we see the lime, but we do not see the carbonic acid.
If, on the other hand, you were to powder a little chalk and drop it into
a good deal of strong vinegar, there would be a great bubbling and
fizzing, and, finally, a clear liquid, in which no sign of chalk would
appear. Here you see the carbonic acid in the bubbles; the lime,
dissolved in the vinegar, vanishes from sight. There are a great many
other ways of showing that chalk is essentially nothing but carbonic acid
and quicklime. Chemists enunciate the result of all the experiments which
prove this, by stating that chalk is almost wholly composed of "carbonate
of lime."
It is desirable for us to start from the knowledge of this fact, though
it may not seem to help us very far towards what we seek. For carbonate
of lime is a widely-spread substance, and is met with under very various
conditions. All sorts of limestones are composed of more or less pure
carbonate of lime. The crust which is often deposited by waters which
have drained through limestone rocks, in the form of what are called
stalagmites and stalactites, is carbonate of lime. Or, to take a more
familiar example, the fur on the inside of a tea-kettle is carbonate of
lime; and, for anything chemistry tells us to the contrary, the chalk
might be a kind of gigantic fur upon the bottom of the earth-kettle,
which is kept pretty hot below.
Let us try another method of making the chalk tell us its own history. To
the unassisted eye chalk looks simply like a very loose and open kind of
stone. But it is possible to grind a slice of chalk down so thin that you
can see through it--until it is thin enough, in fact, to be examined with
any magnifying power that may be thought desirable. A thin slice of the
fur of a kettle might be made in the same way. If it were examined
microscopically, it would show itself to be a more or less distinctly
laminated mineral substance, and nothing more.
But the slice of chalk presents a totally different appearance when
placed under the microscope. The general mass of it is made up of very
minute granules; but, imbedded in this matrix, are innumerable bodies,
some smaller and some larger, but, on a rough average, not more than a
hundredth of an inch in diameter, having a well-defined shape and
structure. A cubic inch of some specimens of chalk may contain hundreds
of thousands of these bodies, compacted together with incalculable
millions of the granules.
The examination of a transparent slice gives a good notion of the manner
in which the components of the chalk are arranged, and of their relative
proportions. But, by rubbing up some chalk with a brush in water and then
pouring off the milky fluid, so as to obtain sediments of different
degrees of fineness, the granules and the minute rounded bodies may be
pretty well separated from one another, and submitted to microscopic
examination, either as opaque or as transparent objects. By combining the
views obtained in these various methods, each of the rounded bodies may
be proved to be a beautifully-constructed calcareous fabric, made up of a
number of chambers, communicating freely with one another. The chambered
bodies are of various forms. One of the commonest is something like a
badly-grown raspberry, being formed of a number of nearly globular
chambers of different sizes congregated together. It is called
_Globigerina_, and some specimens of chalk consist of little else than
_Globigerinoe_ and granules. Let us fix our attention upon the
_Globigerina_. It is the spoor of the game we are tracking. If we can
learn what it is and what are the conditions of its existence, we shall
see our way to the origin and past history of the chalk.
A suggestion which may naturally enough present itself is, that these
curious bodies are the result of some process of aggregation which has
taken place in the carbonate of lime; that, just as in winter, the rime
on our windows simulates the most delicate and elegantly arborescent
foliage--proving that the mere mineral water may, under certain
conditions, assume the outward form of organic bodies--so this mineral
substance, carbonate of lime, hidden away in the bowels of the earth, has
taken the shape of these chambered bodies. I am not raising a merely
fanciful and unreal objection. Very learned men, in former days, have
even entertained the notion that all the formed things found in rocks are
of this nature; and if no such conception is at present held to be
admissible, it is because long and varied experience has now shown that
mineral matter never does assume the form and structure we find in
fossils. If any one were to try to persuade you that an oyster-shell
(which is also chiefly composed of carbonate of lime) had crystallized
out of sea-water, I suppose you would laugh at the absurdity. Your
laughter would be justified by the fact that all experience tends to show
that oyster-shells are formed by the agency of oysters, and in no other
way. And if there were no better reasons, we should be justified, on like
grounds, in believing that _Globigerina_ is not the product of anything
but vital activity.
Happily, however, better evidence in proof of the organic nature of the
_Globigerinoe_ than that of analogy is forthcoming. It so happens that
calcareous skeletons, exactly similar to the _Globigerinoe_ of the chalk,
are being formed, at the present moment, by minute living creatures,
which flourish in multitudes, literally more numerous than the sands of
the sea-shore, over a large extent of that part of the earth's surface
which is covered by the ocean.
The history of the discovery of these living _Globigerinoe_, and of the
part which they play in rock building, is singular enough. It is a
discovery which, like others of no less scientific importance, has
arisen, incidentally, out of work devoted to very different and
exceedingly practical interests. When men first took to the sea, they
speedily learned to look out for shoals and rocks; and the more the
burthen of their ships increased, the more imperatively necessary it
became for sailors to ascertain with precision the depth of the waters
they traversed. Out of this necessity grew the use of the lead and
sounding line; and, ultimately, marine-surveying, which is the recording
of the form of coasts and of the depth of the sea, as ascertained by the
sounding-lead, upon charts.
At the same time, it became desirable to ascertain and to indicate the
nature of the sea-bottom, since this circumstance greatly affects its
goodness as holding ground for anchors. Some ingenious tar, whose name
deserves a better fate than the oblivion into which it has fallen,
attained this object by "arming" the bottom of the lead with a lump of
grease, to which more or less of the sand or mud, or broken shells, as
the case might be, adhered, and was brought to the surface. But, however
well adapted such an apparatus might be for rough nautical purposes,
scientific accuracy could not be expected from the armed lead, and to
remedy its defects (especially when applied to sounding in great depths)
Lieut. Brooke, of the American Navy, some years ago invented a most
ingenious machine, by which a considerable portion of the superficial
layer of the sea-bottom can be scooped out and brought up from any depth
to which the lead descends. In 1853, Lieut. Brooke obtained mud from the
bottom of the North Atlantic, between Newfoundland and the Azores, at a
depth of more than 10,000 feet, or two miles, by the help of this
sounding apparatus. The specimens were sent for examination to Ehrenberg
of Berlin, and to Bailey of West Point, and those able microscopists
found that this deep-sea mud was almost entirely composed of the
skeletons of living organisms--the greater proportion of these being just
like the _Globigerinoe_ already known to occur in the chalk.
Thus far, the work had been carried on simply in the interests of
science, but Lieut. Brooke's method of sounding acquired a high
commercial value, when the enterprise of laying down the telegraph-cable
between this country and the United States was undertaken. For it became
a matter of immense importance to know, not only the depth of the sea
over the whole line along which the cable was to be laid, but the exact
nature of the bottom, so as to guard against chances of cutting or
fraying the strands of that costly rope. The Admiralty consequently
ordered Captain Dayman, an old friend and shipmate of mine, to ascertain
the depth over the whole line of the cable, and to bring back specimens
of the bottom. In former days, such a command as this might have sounded
very much like one of the impossible things which the young Prince in the
Fairy Tales is ordered to do before he can obtain the hand of the
Princess. However, in the months of June and July, 1857, my friend
performed the task assigned to him with great expedition and precision,
without, so far as I know, having met with any reward of that kind. The
specimens or Atlantic mud which he procured were sent to me to be
examined and reported upon.[1]
[Footnote 1: See Appendix to Captain Dayman's _Deep-sea Soundings in the
North Atlantic Ocean between Ireland and Newfoundland, made in H.M.S.
"Cyclops_." Published by order of the Lords Commissioners of the
Admiralty, 1858. They have since formed the subject of an elaborate
Memoir by Messrs. Parker and Jones, published in the _Philosophical
Transactions_ for 1865.]