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point at which documentary evidence fails us； could have no
existence； except for our well grounded confidence that
monuments and works of art or artifice； have never been produced
by causes different in kind from those to which they now owe
their origin。 And geology； which traces back the course of
history beyond the limits of archaeology； could tell us nothing
except for the assumption that； millions of years ago； water；
heat； gravitation； friction； animal and vegetable life； caused
effects of the same kind as they now cause。 Nay； even physical
astronomy； in so far as it takes us back to the uttermost point
of time which palaetiological science can reach； is founded upon
the same assumption。 If the law of gravitation ever failed to be
true； even to a small extent； for that period； the calculations
of the astronomer have no application。
The power of prediction； of prospective prophecy； is that which
is commonly regarded as the great prerogative of physical
science。 And truly it is a wonderful fact that one can go into a
shop and buy for a small price a book； the 〃Nautical Almanac；〃
which will foretell the exact position to be occupied by one of
Jupiter's moons six months hence； nay； more； that； if it were
worth while； the Astronomer…Royal could furnish us with as
infallible a prediction applicable to 1980 or 2980。
But astronomy is not less remarkable for its power of
retrospective prophecy。
Thales； oldest of Greek philosophers； the dates of whose
birth and death are uncertain； but who flourished about 600
B。C。； is said to have foretold an eclipse of the sun which took
place in his time during a battle between the Medes and the
Lydians。 Sir George Airy has written a very learned and
interesting memoir in which he proves that such an eclipse
was visible in Lydia on the afternoon of the 28th of May in the
year 585 B。C。
No one doubts that； on the day and at the hour mentioned by the
Astronomer…Royal； the people of Lydia saw the face of the sun
totally obscured。 But； though we implicitly believe this
retrospective prophecy； it is incapable of verification。 In the
total absence of historical records； it is impossible even to
conceive any means of ascertaining directly whether the eclipse
of Thales happened or not。 All that can be said is； that the
prospective prophecies of the astronomer are always verified；
and that； inasmuch as his retrospective prophecies are the
result of following backwards； the very same method as that
which invariably leads to verified results； when it is worked
forwards； there is as much reason for placing full confidence in
the one as in the other。 Retrospective prophecy is therefore a
legitimate function of astronomical science； and if it is
legitimate for one science it is legitimate for all；
the fundamental axiom on which it rests； the constancy of the
order of nature； being the common foundation of all scientific
thought。 Indeed； if there can be grades in legitimacy； certain
branches of science have the advantage over astronomy； in so far
as their retrospective prophecies are not only susceptible of
verification； but are sometimes strikingly verified。
Such a science exists in that application of the principles of
biology to the interpretation of the animal and vegetable
remains imbedded in the rocks which compose the surface of the
globe； which is called Palaeontology。
At no very distant time； the question whether these so…called
〃fossils；〃 were really the remains of animals and plants was
hotly disputed。 Very learned persons maintained that they were
nothing of the kind； but a sort of concretion； or
crystallisation； which had taken place within the stone in which
they are found； and which simulated the forms of animal and
vegetable life； just as frost on a window…pane imitates
vegetation。 At the present day； it would probably be impossible
to find any sane advocate of this opinion； and the fact is
rather surprising； that among the people from whom the circle…
squarers； perpetual…motioners； flat…earthed men and the like；
are recruited； to say nothing of table…turners and spirit…
rappers； somebody has not perceived the easy avenue to
nonsensical notoriety open to any one who will take up the
good old doctrine； that fossils are all lusus naturae。
The position would be impregnable； inasmuch as it is quite
impossible to prove the contrary。 If a man choose to maintain
that a fossil oyster shell； in spite of its correspondence； down
to every minutest particular； with that of an oyster fresh taken
out of the sea； was never tenanted by a living oyster； but is a
mineral concretion； there is no demonstrating his error。
All that can be done is to show him that； by a parity of
reasoning； he is bound to admit that a heap of oyster shells
outside a fishmonger's door may also be 〃sports of nature；〃 and
that a mutton bone in a dust…bin may have had the like origin。
And when you cannot prove that people are wrong； but only that
they are absurd； the best course is to let them alone。
The whole fabric of palaeontology； in fact； falls to the ground
unless we admit the validity of Zadig's great principle； that
like effects imply like causes； and that the process of
reasoning from a shell； or a tooth； or a bone； to the nature of
the animal to which it belonged； rests absolutely on the
assumption that the likeness of this shell； or tooth； or bone；
to that of some animal with which we are already acquainted； is
such that we are justified in inferring a corresponding degree
of likeness in the rest of the two organisms。 It is on this very
simple principle； and not upon imaginary laws of
physiological correlation； about which； in most cases； we know
nothing whatever； that the so…called restorations of the
palaeontologist are based。
Abundant illustrations of this truth will occur to every one who
is familiar with palaeontology； none is more suitable than the
case of the so…called Belemnites。 In the early days of
the study of fossils； this name was given to certain elongated
stony bodies； ending at one extremity in a conical point； and
truncated at the other； which were commonly reputed to be
thunderbolts； and as such to have descended from the sky。
They are common enough in some parts of England； and； in the
condition in which they are ordinarily found； it might be
difficult to give satisfactory reasons for denying them to be
merely mineral bodies。
They appear； in fact； to consist of nothing but concentric
layers of carbonate of lime； disposed in subcrystalline fibres；
or prisms； perpendicular to the layers。 Among a great number of
specimens of these Belemnites； however； it was soon observed
that some showed a conical cavity at the blunt end； and； in
still better preserved specimens； this cavity appeared to be
divided into chambers by delicate saucer…shaped partitions；
situated at regular intervals one above the other。 Now there is
no