CHAPTER IX.

THE EUROPEAN AGE OF REASON--(_Continued_).

HISTORY OF THE EARTH.--HER SUCCESSIVE CHANGES IN THE COURSE OF TIME.

_Oriental and Occidental Doctrines respecting the Earth in

Time.--Gradual Weakening of the latter by astronomical Facts, and the

Rise of Scientific Geology._

_Impersonal Manner in which the Problem was eventually solved, chiefly

through Facts connected with Heat._

_Proofs of limitless Duration from inorganic Facts.--Igneous and Aqueous

Rocks._

_Proofs of the same from organic Facts.--Successive Creations and

Extinctions of living Forms, and their contemporaneous Distribution._

_Evidences of a slowly declining Temperature, and, therefore, of a long

Time.--The Process of Events by Catastrophe and by Law.--Analogy of

Individual and Race Development.--Both are determined by unchangeable

Law._

_Conclusion that the Plan of the Universe indicates a Multiplicity of

Worlds of infinite Space, and a Succession of Worlds in infinite Time._

[Sidenote: Age of the earth.] A victory could not be more complete nor a

triumph more brilliant than that which had been gained by science in the

contest concerning the position of the earth. Though there followed

closely thereupon an investigation of scarcely inferior moment--that

respecting the age of the earth--so thoroughly was the ancient authority

intellectually crushed that it found itself incapable of asserting by

force the Patristic idea that our planet is less than six thousand years

old.

[Sidenote: The question is impersonally solved.] Not but that a

resistance was made. It was, however, of an indirect kind. The contest

might be likened rather to a partisan warfare than to the deliberate

movement of regular armies under recognized commanders. In its history

there is no central figure like Galileo, no representative man, no

brilliant and opportune event like the invention of the telescope. The

question moves on to its solution impersonally. A little advance is made

here by one, there by another. The war was finished, though no great

battle was fought. In the chapter we are entering upon there is,

therefore, none of that dramatic interest connected with the last.

Impersonally the question was decided, and, therefore, impersonally I

must describe it.

[Sidenote: Oriental and Western doctrines of the age of the earth.] In

Oriental countries, where the popular belief assigns to the creation of

man a very ancient date, and even asserts for some empires a duration of

hundreds of thousands of years, no difficulty as respects the age of the

earth was felt, there seeming to have been time enough for every event

that human researches have detected to transpire. But in the West, where

the doctrine that not only the earth, but the universe itself, was

intended for man, has been carried to its consequences with exacting

rigour, circumstances forbid us to admit that there was any needless

delay between the preparation of the habitation and the introduction of

the tenant. They also force upon us the conclusion that a few centuries

constitute a very large portion of the time of human existence, since,

if we adopt the doctrine of an almost limitless period, we should fall

into a difficulty in explaining what has become of the countless myriads

of generations in the long time so past, and, considering that we are

taught that the end of the world is at hand, and must be expected in a

few years at the most, we might seem to arraign the goodness of God in

this, that He has left to their fate immeasurably the larger proportion

of our race, and has restricted His mercy to us alone, who are living in

the departing twilight of the evening of the world.

[Sidenote: Correction of the European doctrine.] But in this, as in the

former case, a closer examination of the facts brings us to the

indisputable conclusion that we have decided unworthily and untruly;

that our guiding doctrine of the universe being intended for us is a

miserable delusion; that the scale on which the world is constructed as

to time answers to that on which it is constructed as to space; that, as

respects our planet, its origin dates from an epoch too remote for our

mental apprehension; that myriads of centuries have been consumed in its

coming to its present state; that, by a slow progression, it has passed

from stage to stage, uninhabited, and for a long time uninhabitable by

any living thing; that in their proper order and in due lapse of time,

the organic series have been its inhabitants, and of these a vast

majority, whose numbers are so great that we cannot offer an

intelligible estimate of them, have passed away and become extinct, and

that finally, for a brief period, we have been its possessors.

Of the intentions of God it becomes us, therefore, to speak with

reverence and reserve. In those ages when there was not a man upon the

earth, what was the object? Was the twilight only given that the wolf

might follow his fleeing prey, and the stars made to shine that the

royal tiger might pursue his midnight maraudings? Where was the use of

so much that was beautiful and orderly, when there was not a solitary

intellectual being to understand and enjoy? Even now, when we are so

much disposed to judge of other worlds from their apparent adaptedness

to be the abodes of a thinking and responsible order like ourselves, it

may be of service to remember that this earth itself was for countless

ages a dungeon of pestiferous exhalations and a den of wild beasts.

[Sidenote: It elevates rather than degrades the position of man.] It

might moreover appear that the conclusions to which we come, both as

respects the position and age of the world, must necessarily have for

their consequences the diminution and degradation of man, the rendering

him too worthless an object for God's regard. But here again we fall

into an error. True, we have debased his animal value, and taught him

how little he is--how insignificant are the evils, how vain the

pleasures of his life. But, as respects his intellectual principle, how

does the matter stand? What is it that has thus been measuring the

terrestrial world, and weighing it in a balance? What is it that has

been standing on the sun, and marking out the orbits and boundaries of

the solar system? What is it that has descended into the infinite

abysses of space, examined the countless worlds that they contain, and

compared and contrasted them together? What is it that has shown itself

capable of dealing with magnitudes that are infinite, even of comparing

infinites together! What is it that has not hesitated to trace things in

their history through a past eternity, and been found capable of

regarding equally the transitory moment and endless duration? That which

is competent to do all this, so far from being degraded, rises before us

with an air of surpassing grandeur and inappreciable worth. It is the

soul of man.

[Sidenote: Relations of the earth in time.] From the facts given in the

last chapter respecting the relations of the earth in space, we are next

led to her relations in time.

So long as science was oppressed with the doctrine of the human destiny

of the universe, which, as its consequence, made this earth the great

central body, and elevated man to supreme importance, there was much

difficulty in treating the problem of the age of the world. The history

of the earth was at first a wild and fictitious cosmogony. Scientific

cosmogony arose, not from any theological considerations, but from the

telescopic ascertainment of the polar compression of the planet Jupiter,

and the consequent determination by Newton that the earth is a spheroid

of revolution. With a true cosmogony came a better chronology.

[Sidenote: Anthropocentric ideas of the beginning and end of the world.]

The patristic doctrine had been that the earth came into existence but

little more than five thousand years ago, and to this a popular opinion

long current was added, that its end might be very shortly expected.

From time to time periods were set by various authorities determining

the latter event, and, as true knowledge was extinguished, the year 1000

came to be the universally appointed date. In view of this, it was not

an uncommon thing for persons to commence their testamentary bequests

with the words, "In expectation of the approaching end of the world."

But the tremendous moment passed by, and still the sun rose and set,

still the seasons were punctual in their courses, and Nature wore her

accustomed aspect. A later day was then predicted, and again and again

disappointment ensued, until sober-minded men began to perceive that the

Scriptures were never intended to give information on such subjects, and

predictions of the end of the world fell into discredit, abandoned to

the illiterate, whose morbid anticipations they still amuse.

As it was thus with the end of our planet, so it was as regards her

origin. By degrees evidence began to accumulate casting a doubt on her

recent date, evidence continually becoming more and more cogent.

[Sidenote: Rise of the doctrine of illimitable age.] In no insignificant

manner did the establishment of the heliocentric theory, aided by the

discoveries of the telescope, assist in this result. As I have said, it

utterly ruined past restoration the doctrine of the human destiny of the

universe. With that went down all arguments which had depended on making

man the measure of things. Ideas of unexpected sublimity as to the scale

of magnitude on which the world is constructed soon enforced themselves,

and proved to be the precursors of similar ideas as to time. At length

it was perceived by those who were in the van of the movement that the

Bible was never intended to deliver a chronological doctrine respecting

the beginning any more than the end of things, and that those

well-meaning men who were occupied in wresting it from its true purposes

were engaged in an unhappy employment, for its tendency could be no

other than to injure the cause they designed to promote. Nevertheless,

so strong were the ancient persuasions, that it was not without a

struggle that the doctrine of a long period forced its way--a struggle

for the age of the earth, which, in its arguments, in its tendencies,

and in its results, forcibly recalls the preceding one respecting the

position of the earth; but, in the end, truth overrode all authority and

all opposition, and the doctrine of an extremely remote origin of our

planet ceased to be open to dispute.

In a scientific conception of the universe, illimitable spaces are of

necessity connected with limitless time.

[Sidenote: Indications depending on the progressive motion of light.]

The discovery of the progressive motion of light offered the means of an

absolute demonstration of this connexion. Rays emitted by an object, and

making us sensible of its presence by impinging on the eye, do not reach

us instantaneously, but consume a certain period in their passage.

If any sudden visible effect took place in the sun, we should not see it

at the absolute moment of its occurrence, but about eight minutes and

thirteen seconds later, this being the time required for light to cross

the intervening distance. All phenomena take place in reality anterior

to the moment at which we observe them by a time longer in proportion as

the distance to be travelled is greater.

There are objects in the heavens so distant that it would take many

hundreds of thousands of years for their light to reach us. Then it

necessarily follows, since we can see them, that they must have been

created and must have been shining so long.

The velocity with which light moves was first determined by the Danish

astronomer Roemer from the eclipses of Jupiter's satellites, November,

1675. It was, therefore, a determination of the rate for reflected solar

light in a vacuum, and gave 198,000 miles in a second. In 1727, Bradley

determined it for direct stellar light by his great discovery of the

aberration of the fixed stars. More recently, the experiments of M.

Foucault and those of M. Fizeau, by the aid of rotating mirrors or

wheels, have confirmed these astronomical observations, Fizeau's

determination of the velocity approaching that of Roemer. Probably,

however, the most correct is that of Struve, 191,515 miles per second.

[Sidenote: Investigation of the age of the earth through the phenomena

of heat.] This astronomical argument, which serves as a general

introduction, is strengthened by numerous physical and physiological

facts. But of the different methods by which the age of the earth may be

elucidated, I shall prefer that which approaches it through the

phenomena of heat. Such a manner of viewing the problem has led to its

determination in the minds of many thinking men.

[Sidenote: Astronomical heat alone on the earth's surface.] As correct

astronomical ideas began to prevail, it was perceived that all the heat

now on the surface of our planet is derived from the sun. Through the

circumstance of the inclination of her axis of rotation to the plane of

her annual motion, or through the fact of her globular form occasioning

the presentation of different parts of her surface, according to their

latitudes, with more or less obliquity, and hence the reception of less

or more of the rays, there may be local and temporary variations. But

these do not affect the general principle that the quantity of heat thus

received must be the same from year to year.

[Sidenote: The equilibrium of interior heat.] This thermometric

equilibrium not only holds good for the surface, it may also be

demonstrated for the whole mass of the planet. The day has not shortened

by the 1/200 of a second since the time of Hipparchus, and therefore the

decrease of heat can not have been so much as the 1/300 of a Fahrenheit

degree, on the hypothesis that the mean dilatation of all terrestrial

substances is equal to that of glass, 1/180000 for one degree. If a

decline had taken place in the intrinsic heat of the earth, there must

have been a diminution in her size, and, as a necessary consequence, the

length of the day must have become less. The earth has therefore reached

a condition of equilibrium as respects temperature.

[Sidenote: Its ancient decline.] A vast body of evidence has, however,

come into prominence, establishing with equal certainty that there was

in ancient times a far higher temperature in the planet; not a

temperature concerned with a fraction of a degree, but ranging beyond

the limits of our thermometric scale. The mathematical figure of the

earth offers a resistless argument for its ancient liquefied

condition--that is, for its originally high temperature. But how is this

to be co-ordinated with the conclusion just mentioned? Simply by the

admission that there have elapsed prodigious, it might almost be said

limitless, periods. [Sidenote: Necessity for a long time.] As thus the

true state of affairs began to take on shape, it was perceived that the

age of the earth is not a question of authority, not a question of

tradition, but a mathematical problem sharply defined: to determine the

time of cooling of a globe of known diameter and of given conductibility

by radiation in a vacuum.

In such a state of things, what could be more unwise than to attempt to

force opinion by the exercise of authority? How unspeakably mischievous

had proved to be a like course as respects the globular form of the

earth, which did not long remain a mere mathematical abstraction, but

was abruptly brought to a practical issue by the voyage of Magellan's

ship. And on this question of the age of the earth it would have been

equally unwise to become entangled with or committed to the errors of

patristicism--errors arising from well-meant moral considerations, but

which can never exert any influence on the solution of a scientific

problem.

[Sidenote: Indications of the interior heat of the earth.] One fact

after another bearing upon the question gradually emerged into view. It

was shown that the diurnal variations of temperature--that is, those

connected with night and day--extend but a few inches beneath the

surface, the seasonal ones, connected with winter and summer, to many

feet; but beyond this was discovered a stratum of invariable

temperature, beneath which, if we descend, the heat increases at the

rate of 1 deg. Fahr. for every fifty or seventy feet. The uniformity of

this rate seemed to imply that, at depths quite insignificant, a very

high temperature must exist. This was illustrated by such facts that the

water which rushes up from a depth of 1794 feet in the Artesian well of

Grenelle has a temperature of 82 deg. Fahr. The mean temperature of

Paris being about 51 deg. Fahr., these numbers give a rate of 1 deg. for

every fifty-eight feet. If, then, the increase of heat is only 100 deg.

per mile, at a depth of less than ten miles every thing must be red hot,

and at thirty or forty in a melted state. It was by all admitted that

the rise of temperature with the depth is not at all local, but occurs

in whatever part of the earth the observation may be made. The general

conclusion thus furnished was re-enforced by the evidence of volcanoes,

which could no longer be regarded as merely local, depending on

restricted areas for the supply of melted material, since they are found

all over the land and under the sea, in the interior of continents and

near the shores, beneath the equator and in the polar regions. It had

been estimated that there are probably two thousand aerial or subaqueous

eruptions every century. Some volcanoes, as Aetna, have for thousands of

years poured forth their lavas, and still there is an unexhausted

supply. Everywhere a common source is indicated by the rudely uniform

materials ejected. The fact that the lines of volcanic activity shift

pointed to a deep source; the periodic increments and decrements of

force bore the same interpretation. They far transcend the range of

history. The volcanoes of central France date from the Eocene period;

their power increased in the Miocene, and continued through the

Pliocene; those of Catalonia belong to the Pliocene, probably. Coupled

with volcanoes, earthquakes, with their vertical, horizontal, and rotary

vibrations, having a linear velocity of from twenty to thirty miles per

minute, indicated a profound focus of action. The great earthquake of

Lisbon was felt from Norway to Morocco, from Algiers to the West Indies,

from Thuringia to the Canadian lakes. It absolutely lifted the whole bed

of the North Atlantic Ocean. Its origin was in no superficial point.

[Sidenote: Proof from the mean density.] A still more universal proof of

a high temperature affecting the whole mass of the interior of the globe

was believed to be presented in the small mean density of the earth, a

density not more than 5.66 times that of water, the mean density of the

solid surface being 2.7, and that of the solid and sea-surface together

1.6. But this is not a density answering to that which the earth should

have in virtue of the attraction of her own parts. It implied some agent

capable of rarefying and dilating, and the only such agent is heat.

Although the law of the increase of density from the upper surface to

the centre is unknown, yet a comparison of the earth's compression with

her velocity of rotation demonstrated that there is an increasing

density in the strata as we descend. The great fact, however, which

stands prominently forth is the interior heat.

Not only were evidences thus offered of the existence of a high

temperature, and, therefore, of the lapse of a long time by the present

circumstances of the globe; every trace of its former state, duly

considered, yielded similar indications, the old evidence corroborating

the new. And soon it appeared that this would hold good whether

considered in the inorganic or organic aspect.

[Sidenote: Inorganic proofs of a former high temperature.] In the

inorganic, what other interpretation could be put on the universal

occurrence of igneous rocks, some in enormous mountain ranges, some

ejected from beneath, forcing their tortuous way through thus resisting

superincumbent strata; veins of various mineral constitution, and, as

their relations with one another showed, veins of very different dates?

What other interpretation of layers of lava in succession, one under

another, and often with old disintegrated material between? What of

those numerous volcanoes which have never been known to show any signs

of activity in the period of history, though they sometimes occur in

countries like France, eminently historic? What meaning could be

assigned to all those dislocations, subsidences, and elevations which

the crust of the earth in every country presents, indications of a loss

of heat, of a contraction in diameter, and its necessary consequence,

fracture of the exterior consolidated shell along lines of least

resistance? And though it was asserted by some that the catastrophes of

which these are the evidences were occasioned by forces of unparalleled

energy and incessant operation--unparalleled when compared with such

terrestrial forces as we are familiar with--that did not, in any

respect, change the interpretation, for there could have been no abrupt

diminution in the intensity of those forces, which, if they had lessened

in power, must have passed through a long, a gradual decline. [Sidenote:

These necessarily imply long time.] In that very decline there thus

spontaneously came forth evidences of a long lapse of time. The whole

course of Nature satisfies us how gradual and deliberate are her

proceedings; that there is no abrupt boundary between the past and the

present, but that the one insensibly shades off into the other, the

present springing gently and imperceptibly out of the past. If volcanic

phenomena and all kinds of igneous manifestations--if dislocations,

injections, the intrusion of melted material into strata were at one

time more frequent, more violent--if, in the old times, mundane forces

possessed an energy which they have now lost, their present diminished

and deteriorated condition, coupled with the fact that for thousands of

years, throughout the range of history, they have been invariably such

as we find them now, should be to us a proof how long, how very long ago

those old times must have been.

[Sidenote: Support from astronomical facts.] Thus, therefore, was

perceived the necessity of co-ordinating the scale of time with the

scale of space, and such views of the physical history of the earth were

extended to celestial bodies which were considered as having passed

through a similar course. In one, at least, this assertion was no mere

matter of speculation, but of actual observation. The broken surface of

the moon, its volcanic cones and craters, its mountains, with their

lava-clad sides and ejected blocks glistening in the sun, proved a

succession of events like those of the earth, and demonstrated that

there is a planetary as well as a terrestrial geology, and that in our

satellite there is evidence of a primitive high temperature, of a

gradual decline, and, therefore, of a long process of time. Perhaps

also, considering the rate of heat-exchange in Venus by reason of her

proximity to the sun, the pale light which it is said has been observed

on her non-illuminated part is the declining trace of her own intrinsic

temperature, her heat lasting until now.

[Sidenote: Astronomical facts imply slow secular changes.] If

astronomers sought in systematic causes an explanation of these facts

if, for instance, they were disposed to examine how far changes in the

obliquity of the ecliptic are connected therewith--it was necessary at

the outset to concede that the scale of time on which the event proceeds

is of prodigious duration, this secular variation observing a slow

process of only 45.7'' in a century; and hence, since the time of

Hipparchus, two thousand years ago, the plane of the ecliptic has

approached that of the equator by only a quarter of a degree. Or if,

again, they looked to a diminishing of the eccentricity of the earth's

orbit, they were compelled to admit the same postulate, and deal with

thousands of centuries. Under whatever aspect, then, the theory was

regarded, if once a former high temperature were admitted, and the fact

coupled therewith that there has been no sensible decline within the

observation of man, whether the explanation was purely geological or

purely astronomical, the motion of heat in the mass of the earth is so

slow, yet the change that has taken place is so great, the variations of

the contemplated relations of the solar system so gradual--under

whatever aspect and in whatever way the fact was dealt with, there arose

the indispensable concession of countless centuries.

To the astronomer such a concession is nothing extraordinary. It is not

because of the time required that he entertains any doubt that the sun

and his system accomplish a revolution round a distant centre of gravity

in nineteen millions of years, or that the year of epsilon Lyrae is

half a million of ours. He looks forward to that distant day when Sirius

will disappear from our skies, and the Southern Cross be visible, and

Vega the polar star. He looks back to the time when gamma Draconis

occupied that conspicuous position, and the builders of the great

pyramid, B.C. 3970, gave to its subterranean passage an inclination of

26 deg. 15', corresponding to the inferior culmination of that star. He

tells us that the Southern Cross began to be invisible in 52 deg. 30' N.,

2900 years before our era, and that it had previously attained an

altitude of more than 10 deg.. When it disappeared from the horizon of

the countries on the Baltic, the pyramid of Cheops had been erected more

than a thousand years.

[Sidenote: Proofs of time from aqueous effects,] We must pass by a

copious mass of evidence furnished by aqueous causes of change operating

on the earth's surface, though these add very weighty proof to the

doctrine of a long period. The filling up of lakes, the formation of

deltas, the cutting power of running water, the deposit of travertines,

the denudation of immense tracts of country, the carrying of their

detritus into the sea, the changes of shores by tides and waves, the

formation of strata hundreds of miles in length, and the imbedding

therein of fossil remains in numbers almost beyond belief, furnished

many interesting and important facts. Of these not a few presented means

of computation. It would not be difficult to assign a date for such

geographical events as the production of the Caspian and Dead Seas from

an examination of the sum of saline material contained in their waters

and deposited in their bed, with the annual amount brought into them by

their supplying rivers. Such computations were executed as respects the

growth of Lower Egypt and the backward cutting of Niagara Falls, and,

though they might be individually open to criticism, their mutual

accordance and tendency furnished an evidence that could not be

gainsaid. The continual accumulation of such evidence ought not to be

without its weight on those who are still disposed to treat slightingly

the power of geological facts in developing truth.

[Sidenote: and from the movements of the earth's crust.] To such facts

were added all those, with which volumes might be filled, proving the

universality of the movements of the solid crust of the earth--strata

once necessarily horizontal now inclined at all angles, strata

unconformable to one another--a body of evidence most copious and most

satisfactory, yet demonstrating from the immensity of the results how

slowly the work had gone on.

How was it possible to conceive that beds many hundred feet in thickness

should have been precipitated suddenly from water? Their mechanical

condition implied slow disintegration and denudation in other localities

to furnish material; their contents showed no trace of violence; they

rather proved the deposition to have occurred in a tranquil and quiet

way. What interpretation could be put upon facts continually increasing

in number like those observed in the south-east of England, where

fresh-water beds a thousand feet thick are covered by other beds a

thousand feet thick, but of marine origin? What upon those in the north

of England, where masses once uplifted a thousand feet above the level,

and, at the time of their elevation, presenting abrupt precipices and

cliffs of that height, as is proved by the fractures and faults of the

existing strata, have been altogether removed, and the surface left

plain? In South Wales there are localities where 11,000 feet in

thickness have been bodily carried away. Whether, therefore, the strata

that have been formed, and which remain to strike us with astonishment

at their prodigious mass, were considered; or those that have been

destroyed, not, however, without leaving unmistakable traces of

themselves; the processes of wearing away to furnish material as well as

the accumulation, of necessity required the lapse of long periods of

time. The undermining of cliffs by the beating of the sea, the

redistribution of sands and mud at the bottom of the ocean, the washing

of material from hills into the lowlands by showers of rain, its

transport by river courses, the disintegration of soils by the influence

of frost, the weathering of rocks by carbonic acid, and the solution of

limestone by its aid in water--these are effects which, even at the

quickest, seem not to amount to much in the course of the life of a man.

A thousand years could yield but a trifling result.

We have already alluded to another point of view from which these

mechanical effects were considered. The level of the land and sea has

unmistakably changed. There are mountain eminences ten or fifteen

thousand feet in altitude in the interior of continents over which, or

through which shells and other products of the sea are profusely

scattered. And though, considering the proverbial immobility of the

solid land and the proverbial instability of the water, it might at

first be supposed much more likely that the sea had subsided than that

the land had risen, a more critical examination soon led to a change of

opinion. Before our eyes, in some countries, elevations and depressions

are taking place, sometimes in a slow secular manner, as in Norway and

Sweden, that peninsula on the north rising, and on the south sinking, at

such a rate that, to accomplish the whole seven hundred feet of

movement, more than twenty-seven thousand years would be required if it

had always been uniform as now. Elsewhere, as on the south-western coast

of South America, the movement is paroxysmal, the shore line lifting for

hundreds of miles instantaneously, and then pausing for many years. In

the Morea also, range after range of old sea cliffs exist, some of them

more than a thousand feet high, with terraces at the base of each; but

the Morea has been well known for the last twenty-five centuries, and in

that time has undergone no material change. Again, in Sicily, similar

interior sea-cliffs are seen, the rubbish at their bases containing the

bones of the hippopotamus and mammoth, proofs of the great change the

climate has undergone since the sea washed those ancient beaches. Italy,

pre-eminently the historic country, in which, within the memory of man,

no material change of configuration has taken place since the

Pleistocene period, very late geologically speaking has experienced

elevations of fifteen hundred feet. The seven hills of Rome are of the

Pliocene, with fluviatile deposits and recent terrestrial shells two

hundred feet above the Tiber. There intervened between the older

Pliocene and the newer a period of enormous length, as is demonstrated

by the accumulated effects taking place in it, and, indeed, the same may

be said of every juxtaposed pair of distinctly marked strata. It

demanded an inconceivable time for beds once horizontal at the bottom of

the sea to be tilted to great inclinations; it required also the

enduring exertion of a prodigious force. Ascent and descent may be

detected in strata of every age: movements sometimes paroxysmal, but

more often of tranquil and secular kind. The coal-bearing strata, by

gradual submergence, attained in South Wales a thickness of 12,000 feet,

and in Nova Scotia, a total thickness of 14,570 feet; the uniformity of

the process of submergence and its slow steadiness is indicated by the

occurrence of erect trees at different levels: seventeen such

repetitions may be counted in a thickness of 4515 feet. The age of the

trees is proved by their size, some being four feet in diameter. Round

them, as they gradually went down with the subsiding soil, calamites

grew at one level after another. In the Sidney coal-field fifty-nine

fossil forests thus occur in superposition.

[Sidenote: Organic proofs of a former high temperature.] Such was the

conclusion forcing itself from considerations connected with inorganic

nature. It received a most emphatic endorsement from the organic world,

for there is an intimate connexion between the existence and well-being

both of plants and animals, and the heat to which they are exposed. Why

is it that the orange and lemon do not grow in New York? What is it that

would inevitably ensue if these exotics were exposed to a cold winter?

What must take place if, in Florida or other of the Southern states, a

season of unusual rigor should occur? Does not heat thus confine within

a fixed boundary the spread of these plants? And so, again, how many

others there are which grow luxuriantly in a temperate climate, but are

parched up and killed if fortuitously carried beneath a hot tropical

sun. To every one there is a climate which best suits the condition of

its life, and certain limits of heat and cold beyond which its existence

is not possible.

If the mean annual heat of the earth's surface were slowly to rise, and,

in the course of some centuries, the temperature now obtaining in

Florida should obtain in New York, the orange and lemon would certainly

be found here. [Sidenote: Boundary of organisms by heat.] With the

increasing heat those plants would commence a northward march, steadily

advancing as opportunity was given. Or, if the reverse took place, and

for any reason the heat of the torrid zone declined until the winter's

cold of New York should be at last reached under the equator, as the

descent went on the orange and lemon would retreat within a narrow and

narrower region, and end by becoming extinct, the conditions of their

exposure being incompatible with the continuance of their life. From

such considerations it is therefore obvious that not only does heat

arrange the limits of the distribution of plants, erecting round them

boundaries which, though invisible, are more insuperable than a wall of

brass, it also regulates their march, if march there is to be--nay, even

controls their very existence, and to genera, and species, and

individuals appoints a period of duration.

[Sidenote: Animals localized as well as plants.] Such observations apply

not alone to plants; the animal kingdom offers equally significant

illustrations. Why does the white bear enjoy the leaden sky of the pole

and his native iceberg? Why does the tiger restrict himself to the

jungles of India? Can it be doubted that, if the mean annual temperature

should decline, the polar bear would come with his iceberg to

corresponding southern latitudes, or, if the heat should rise, the tiger

would commence a northward journey? Does he not, indeed, every summer

penetrate northward in Asia as far as the latitude of Berlin, and retire

again as winter comes on? Why is it that, at a given signal, the birds

of passage migrate, pressed forward in the spring by the heat, and

pressed backward in the autumn by the cold? The annual migration of

birds illustrates the causes of geological appearances and extinctions.

Do we not herein recognize the agent that determines animal

distribution? We must not deceive ourselves with any fancied terrestrial

impediment or restraint. Let the heat rise but a few degrees, and the

turkey-buzzard, to whose powerful wing distances are of no moment and

the free air no impediment, would be seen hovering over New York; let it

fall a few degrees, and he would vanish from the streets of Charleston;

let it fall a little more, and he would vanish from the earth.

Shell-fish, once the inhabitants of the British seas, retired during the

glacial period to the Mediterranean, and with the returning warmth have

gone back northward again.

[Sidenote: Control of animals by food.] Animals are thus controlled by

heat in an indirect as well as a direct way. Indirectly; for, if their

food be diminished, they must seek a more ample supply; if it fails,

they must perish. Doubtless it was insufficient food, as well as the

setting in of a more rigorous climate, that occasioned the destruction

of the mastodon giganteus, which abounded in the United States after the

drift period. Such great elephantine forms could not possibly sustain

themselves against the rigors of the present winters, nor could they

find a sufficient supply of food for a considerable portion of the year.

The disappearance of animals from the face of the earth was, as

Palaeontology advanced, ascertained to have been a determinate process, a

condition of their existence, and either inherent in themselves or

dependent on their environment. It was proved that the forms now

existing are only an insignificant part of the countless tribes that

have lived. [Sidenote: Nature of creations and extinctions.] The earth

has been the theatre of a long succession of appearances and removals,

of creations and extinctions, reaching to the latest times. In the

Pleistocene of Sicily, 35/124 of the fossil shells are extinct; in the

bone caverns of England, out of thirty-seven mammals eighteen are

extinct. But judging, from what may be observed of the duration of races

contemporary with us, that their life is prolonged for thousands of

years, successive generations of the same species in a long order

replacing their predecessors before final removal occurs, this again

resistlessly brought forward the same conclusion to which all the

foregoing facts had pointed, that there have transpired since the

introduction of animal life upon this globe very long periods of time.

Through the operation of this law of extinction and of creation,

animated nature, both on the continents and in the seas, has undergone a

marvellous change. In the lias and oolitic seas, the Enaliosauria,

Cetiosauria, and Crocodilia dominated as the Delphinidae and Balaenidae do

in ours; the former have been eliminated, the latter produced. Along

with the cetaceans came the soft-scaled Cycloid and Ctenoid fishes,

orders which took the place of the Ganoids and Placoids of the Mesozoic

times. One after another successive species of air-breathing reptiles

have emerged, continued for their appointed time to exist, and then died

out. The development has been, not in the descending, but in the

ascending order; the Amphitheria, Spalacotheria, Triconodon of the

Mesozoic times were substituted by higher tertiary forms. Nor have these

mutations been abrupt. If mammals are the chief characteristic of the

Tertiary ages, their first beginnings are seen far earlier; in the

triassic and oolitic formations there are a few of the lower orders

struggling, as it were, to emerge. The aspect of animated nature has

altogether changed. No longer does the camelopard wander over Europe as

he did in the Miocene and Pliocene times; no longer are great elephants

seen in the American forests, the hippopotamus in England, the

Rhinoceros in Siberia. The hand of man has introduced in the New the

horse of the Old World; but the American horse, that ran on the great

plains contemporary with the megatherium and megalonyx, has for tens of

thousands of years been extinct. Even the ocean and the rivers are no

exception to these changes.

[Sidenote: Creations and extinctions by law.] What, then, is the manner

of origin of this infinite succession of forms? It is often sufficient

to see clearly a portion of a plan to be able to determine with some

degree of certainty the general arrangement of the whole; it is often

sufficient to know with precision a part of the life of an individual to

guess with probable accuracy his action in some forthcoming event, of to

determine the share he has borne in affairs that are past. It is enough

to appreciate thoroughly the style of a master to ascertain without

doubt the authenticity of an imputed picture. And so, in the affairs of

the universe, it is enough to ascertain the manner of operation of a

part in order to settle the manner of operation of the whole. When,

therefore, it was perceived how the disappearance of vanishing forms

from the surface of the globe is accomplished--that it is not by a

sudden and grand providential intervention--that there is no visible

putting forth of the Omnipotent hand, but slowly and silently, yet

surely, the ordinary laws of Nature are permitted to take their

course--that heat, and cold, and want of food, and dryness, and

moisture, in the end, as if by an irresistible destiny, accomplish the

event, it seemed to indicate that, as regards the introduction of

new-comers, a suitableness of external conditions had called them forth,

as an unsuitableness could end them. Changes in the constitution of the

air or its pressure, in the composition of the sea or its depth, in the

brilliancy of light or the amount of heat, in the inorganic material of

a medium, will modify old forms into new ones, or compel their

extinction. Birth and death go hand in hand; creation and extinction are

inseparable. The variation of organic form is continuous; it depends

upon an orderly succession of material events; appearances and

eliminations are managed upon a common principle; they stand connected

with the irresistible course of great mundane changes. It was impossible

that geologists could reach any other conclusion than that such

phenomena are not the issue of direct providential interventions, but of

physical influences. The procession of organic life is not a motley

march; it follows the procession of physical events; and, since it is

impossible to re-establish a sameness of physical conditions that have

once come to an end, or reproduce the order in which they have occurred,

it of necessity follows that no organic form can reappear after it has

once died out--once dead, it is clean gone for ever.

[Sidenote: Interstitial molecular creations.] In the course of the life

of individual man, the parts that constitute his system are undergoing

momentary changes; those of to-day are not the same as those of

yesterday, and they will be replaced by others to-morrow. There have

been, and are every instant, interstitial deaths of all the constituent

particles, and an unceasing removal of those that have performed their

duty. In the stead of departing portions, new ones have been introduced,

interstitial births and organizations perpetually taking place. In

physiology it became no longer a question that all this proceeds in a

determinate way under the operation of principles that are fixed, of

laws that are invariable. The alchemists introduced no poetical fiction

when they spoke of the microcosm, asserting that the system of man is

emblematical of the system of the world. The intercalation of a new

organic molecule in a living being answers to the introduction of a new

form in the universal organic series. It requires as much power to call

into existence a living molecule as to produce a living being. Both are

accomplished upon the same principle, and that principle is not an

incessant intervention of a supernatural kind, but the operation of

unvarying law. Physical agents, working through physical laws, remove in

organisms such molecules as have accomplished their work and create new

ones, and physical agents, working through physical laws, control the

extinctions and creations of forms in the universe of life. The

difference is only in the time. What is accomplished in the one case in

the twinkling of an eye, in the other may demand the lapse of a thousand

centuries.

[Sidenote: Defence of the process of all things by law.] The variation

of organic forms, under the force of external circumstances, is thus

necessary to be understood in connexion with that countless succession

of living beings demonstrated by geology. It carries us, in common with

so much other evidence, to the lapse of a long time. Nor are such views

as those to which we are thus constrained inconsistent with the

admission of a Providential guidance of the world. Man, however learned

and pious he may be, is not always a trustworthy interpreter of the ways

of God. In deciding whether any philosophical doctrine is consistent or

inconsistent with the Divine attributes, we are too prone to judge of

those attributes by our own finite and imperfect standard, forgetting

that the only test to which we ought to resort is the ascertainment if

the doctrine be true. If it be true, it is in unison with God. Perhaps

some who have rejected the conception of the variation of organic forms,

with its postulate--limitless duration, may have failed to remember the

grandeur of the universe and its relations to space and to time; perhaps

they do not recall the system on which it is administered. Like the

anthropomorphite monks of the Nile, they conceive of God as if he were

only a very large man; else how could it for a moment have been doubted

that it is far more--I use the expression reverently--in the style of

the great Constructor to carry out his intentions by the summary

operations of law? It might be consistent with the weakness and

ignorance of man to be reduced to the necessity of personal intervention

for the accomplishment of his plans, but would not that be the very

result of such ignorance? Does not absolute knowledge actually imply

procedure by preconceived and unvarying law? Is not momentary

intervention altogether derogatory to the thorough and absolute

sovereignty of God? The astronomical calculation of ancient events, as

well as the prediction of those to come, is essentially founded on the

principle that there has not in the times under consideration, and that

there will never be in the future, any exercise of an arbitrary or

overriding will. The corner-stone of astronomy is this, that the solar

system--nay, even the universe, is ruled by necessity. To operate by

expedients is for the creature, to operate by law for the Creator; and

so far from the doctrine that creations and extinctions are carried on

by a foreseen and predestined ordinance--a system which works of itself

without need of any intermeddling--being an unworthy, an ignoble

conception, it is completely in unison with the resistless movements of

the mechanism of the universe, with whatever is orderly, symmetrical,

and beautiful upon earth, and with all the dread magnificence of the

heavens.

[Sidenote: Historical sketch of early Palaeontology.] It was in Italy

that particular attention was first given to organic remains. Leonardo

da Vinci asserts that they are real shells, or the remains thereof, and

hence that the land and sea must have changed their relative position.

At this time fossils were looked upon as rare curiosities, no one

supposing that they were at all numerous, and many were the fantastic

hypotheses proposed to account for their occurrence. Some referred them

to the general deluge mentioned in Scripture; some to a certain plastic

power obscurely attributed to the earth; some thought that they were

engendered by the sunlight, heat, and rain. To Da Vinci is due the first

clear assertion of their true nature, that they are actually the remains

of organic beings. Soon the subject was taken up by other eminent

Italians. Fracaster wrote on the petrifactions of Verona; Scilla, a

Sicilian, on marine bodies turned into stone, illustrating his work by

engravings. Still later, Vallisneri, 1721, published letters on marine

bodies found in rocks, attempting by their aid to determine the extent

of the marine deposits of Italy. These early cultivators of geology soon

perceived the advantage to be gained by the establishment of museums and

the publication of catalogues. The first seems to have been that of John

Kentman, an example that was followed by Calceolarius and Vallisneri.

Subsequently Fontanelle proposed the construction of charts in

accordance with fossil remains; but the principle involved was not

applied on the great scale as a true geological test until introduced by

Smith in connexion with the English strata.

[Sidenote: The pre-organic time.] To Steno, a Dane, is due the

recognition of pre-organic in contradistinction to organic rocks, a

distinction the terms of which necessarily involve the idea of time.

Soon it became generally recognized that the strata in which organic

remains occur are of a later date than those devoid of them, the

pre-organic rocks demonstrating a pre-organic time. Moreover, as facts

were developed, it was plain that there are essential differences in the

relations of fossils, and that, though in Italy the same species of

shells may occur in the mountains that occur in the adjacent seas, this

was very far from being the case uniformly elsewhere. At length the

truth began to emerge, that in proportion as the strata under

examination are of an older date, so are the differences between their

organic remains and existing species more marked. It was also discovered

that the same species often extends superficially over immense

districts, but that in a vertical examination one species after another

rapidly appears in a descending order--an order which could be verified

in spite of the contortions, fractures, and displacements of the strata.

A very important theoretical conclusion was here presented: for the

rapid succession of essentially different organic forms, as the rocks

were older, was clearly altogether inconsistent with one catastrophe, as

the universal deluge, to which it had been generally referred. It was

plain that the thickness of the strata in which they were enveloped, and

the prodigious numbers in which they occurred, answered in some degree

to the period of life of those fossils, since every one of them, large

or small, must have had its time of birth, of maturity, and of death.

[Sidenote: Insufficiency of a single catastrophe.] When, therefore, it

could be no longer doubted that strata many hundreds of feet in

thickness were crowded with such remains, it became altogether out of

the question to refer their entombment to the confusion of a single

catastrophe, for every thing indicated an orderly and deliberate

proceeding. Still more cogent did this evidence become when, in a more

critical manner, the fossils were studied, and some strata were

demonstrated to be of a fresh-water and others of a marine origin, the

one intercalated with the other like leaves in a book. To this fact may

be imputed the final overthrow of the doctrine of a single catastrophe,

and its replacement by a doctrine of periodical changes.

[Sidenote: The orderly progression of organization.] From these

statements it will therefore be understood that, commencing with the

first appearance of organization, an orderly process was demonstrated

from forms altogether unlike those with which we are familiar, up to

those at present existing, a procedure conducted so slowly that it was

impossible to assign for it a shorter duration than thousands of

centuries. Moreover, it seemed that the guiding condition which had

controlled this secular march of organization was the same which still

determines the possibility of existence and the distribution of life.

The succession of organic forms indicates a clear relation to a

descending temperature. The plants of the earliest times are plants of

an ultratropical climate, and that primitive vegetation seemed to

demonstrate that there had been a uniform climate--a climate of high

temperature--all over the globe. The coal-beds of Nova Scotia exhibited

the same genera and species as those of Europe, and so well marked was

the botanical connexion with the declining temperature in successive

ages that attempts were made to express eras by their prevailing

organisms; thus Brongniart's division is, for the Primary strata, the

Age of Acrogens; the Secondary, exclusive of the Cretaceous, the Age of

Gymnogens; the third, including the Cretaceous and Tertiary, the Age of

Angiosperms. It is to be particularly remarked that the Cretaceous

flora, in the aggregate, combines the antecedent and succeeding periods,

proving that the change was not by crisis or sudden catastrophe, but

that the new forms rose gently among the old ones. After the Eocene

period, dicotyledonous angiosperms became the prevalent form, and from

that date to the Pleistocene the evidences of a continued refrigeration

are absolute.

[Sidenote: Climates in time and in place.] As thus an examination was

made from the most ancient to the later ages, indications were found of

a climate arrangement more and more distinct--in the high latitudes,

from the ultratropical through the tropical, the temperate, down to the

present frigid state; in lower latitudes the declining process stopping

short at an earlier point. It therefore appeared that there has been a

production of climates both in an order of time and, in an order of

locality, the greatest change having occurred in the frigid zone, which

has passed through all mean temperatures, an intermediate change in the

temperate, and a minimum in the torrid zone. The general effect has thus

been to present a succession of surfaces on the same planet adapted to a

varied organization, and offering a more magnificent spectacle than if

we were permitted to inspect many different planets; for in them there

might be no necessary connexion of their forms of life, but in this

there is, so that, were our knowledge of Comparative Physiology more

perfect, we might amuse ourselves with intercalating among the plant and

animal organisms familiar to us hypothetical forms that would make the

series complete, and verify our principles by their subsequent discovery

in the deep strata of the earth.

Does not this progression of life in our planet suggest a like

progression for the solar system, which in its aggregate is passing in

myriads of years through all organic phases? May we not also, from our

solar system, rise to a similar conception for the universe?

There are two very important considerations, on which we must dwell for

the complete understanding of the consequences of these changes: 1st.

The mechanism of the declining temperature; 2d. Its effect in the

organic world.

[Sidenote: The nature of terrestrial declining temperature.] 1st. A

uniformly high temperature could never be manifested all over the

surface of our planet through any heating influence of the sun. A high

and uniform temperature unerringly points to an internal cause; and the

gradual appearance of climates, manifesting a relatively increasing

power of the sun, indicates the slow diminution of that internal heat.

But this is precisely the conclusion which was come to from a

contemplation of the earth from a purely physical point of view. So long

as its intrinsic heat overpowered that derived from the sun, it was not

possible that any thing answering to climates could be established; and,

until a certain degree of cooling by radiation had been accomplished,

the heat must have been comparatively uniform in all latitudes; but,

that point gained, there necessarily ensued an arrangement of zones of

different temperatures, or, in other words, climates appeared, the

process being essentially slow, and becoming slower as the loss of heat

went on. Finally, when loss of heat from the earth ceased, an

equilibrium was reached in the climate arrangement as we now find it.

Thus purely physical as well as geological considerations brought

philosophers on this point to the same conclusion--that conclusion which

has been so often repeated--very long periods of time.

[Sidenote: Consequent effect on the Flora and Fauna.] 2nd. As to the

effect on the organic world. Nothing can live at a temperature higher

than the boiling-point of water, for the condition of life implies that

there shall circulate from part to part of a living mechanism a watery

liquid, sap, or blood. From this it necessarily follows that a planet,

the temperature of which is above a certain limit, must necessarily have

a lifeless surface; and this seemed to be the interpretation of that

pre-organic time to which we have referred. Moreover, when the

temperature suitably descends so as to come within the limit at which

life is possible, its uniformity over the surface of a planet will

produce a sameness in the organization. It would be an identity if heat

were the only regulating condition of life. At this stage of things, the

solar heat being overpowered, and a sensibly uniform temperature in all

latitudes existing, still the only possible organic forms are those

consistent with a high temperature, uniformity in the physical condition

impressing a general uniformity in the aspect of life geographically.

[Sidenote: Production and distribution of new organisms.] But the moment

that climate arrangement has become possible, variety of organic form

becomes possible. Now also ensues another all-important

result--geographical distribution. Both of plants and animals, those

whose vital conditions are inconsistent with the occurring change must

retire from the affected locality. In plants this retrocession is

brought to pass by the gradual sickening and death of individuals, or

the impossibility of reproduction; in animals there is added thereto,

because of their power of locomotion, voluntary retirement, at least in

the case of individuals, and immobility in the species is corrected by

locomotion in the individual. The affected region has become unsuitable,

cheerless, uncomfortable; they abandon it; and as the boundary they

thus, in the one case, can not, and in the other will not overpass,

advances, so do they recede before it. If the change were abrupt, or

took place by a sudden crisis, there would seem to be no other possible

event than an overcrowding of the unaffected region and a desolation of

the part that had varied. But, since a developing cell under a new

condition produces a new form, and since the physical change is taking

place with extreme slowness, the appearance of modified structures

ensues. And thus, by decline of temperature, two distinct results are

accomplished--first the production of organic forms in an order of

succession, new ones replacing the old, as if they were transmutations

of them, and, secondly, geographical distribution.

[Sidenote: Delusive nature of organic equilibrium.] In my "Physiology" I

have endeavoured to explain in detail the principles here set forth. I

have endeavoured to show that the aspect of sameness presented by an

animal or plant is no proof of unchangeability. Those forms retain in

our times their special aspect because the conditions of the theatre in

which they live do not change; but let the mean temperature rise, let

the sun-rays become brighter, change the composition of the air, and

forthwith the world of organization would show how profoundly it was

affected. Nor need such changes, in one sense, be more than

insignificant to produce prodigious results. Thus the air contains only

1/2000 of its volume of carbonic acid gas. That apparently trifling

quantity taken away, in an instant the whole surface of the earth would

become a desolate waste, without the possibility of vegetable life.

[Sidenote: The Coal period.] As physical geology advanced, the Coal

period was perceived to be the chief epoch in the history of our planet.

Through a slow decline of temperature, a possibility had gradually been

attained, so far as the condition of heat was concerned, for a luxuriant

vegetable growth. All that prodigious mass of carbon now found in the

earth in the various forms of coal existed as carbonic acid in the

atmosphere. The proportion of free oxygen was less than at present by a

volume equal to the excess of carbonic acid. [Sidenote: Effects of light

on the atmosphere,] A change in the constitution of this primaeval

atmosphere was occasioned by the action of the light; for, under the

influence of the sun-rays, plants decompose carbonic acid, appropriating

its carbon, and, for the most part, setting the oxygen free. The

quantity of carbon which can thus be condensed for the use of a plant,

and, indeed, every such decomposing action by light, is directly

proportionate to the quantity of light consumed, as experiments which I

have personally made have proved. For the production of so great a

weight of combustible matter a very long period of time was necessarily

required, that the sun might supply the necessary luminous influence.

Age after age the sunbeams continued their work, changing the mechanical

relations and composition of the atmosphere, the constitution of the

sea, and the appearance of the surface of the earth. There was a

prodigious growth of ferns, lepidodendra, equisetaceae, coniferae. The

percentage of oxygen in the air continually increased, that of carbonic

acid continually declined; the pressure of the air correspondingly

diminished, partly because of the replacement of a heavy gas by a

lighter one, and partly because of the general decline of temperature

slowly taking place, which diminished the absolute volume of vapour.

[Sidenote: and also on the sea.] The sea, in its deepest abysses, was

likewise affected by the sunlight; not directly, but in an indirect way;

for, as the removal of carbonic acid from the atmosphere went on,

portions of that gas were perpetually surrendered by the ocean in order

to maintain a diffusion-equilibrium between its dissolved gas and the

free gas of the air. And now no longer could be held in transparent

solution by the water those great quantities of carbonate of lime which

had once been concealed in it, the deposit of a given weight of coal in

the earth being inevitably followed by the deposit of an equivalent

weight of carbonate of lime in the sea. This might have taken place as

an amorphous precipitate; but the probabilities were that it would

occur, as in fact it did, under forms of organization in the great

limestone strata coeval with and posterior to the coal. The air and the

ocean were thus suffering an invisible change through the disturbing

agency of the sun, and the surface of the solid earth was likewise

undergoing a more manifest, and, it may be said, more glorious

alteration. Plants, in wild luxuriance, were developing themselves in

the hot and dank climate, and the possibility was now approaching for

the appearance of animal types very much higher than any that had yet

existed. [Sidenote: Cold-blooded animals succeeded by hot.] In the old

heavy atmosphere, full of a noxious gas, none but slowly-respiring

cold-blooded animals could maintain themselves; but after the great

change in the constitution of the air had been accomplished, the

quickly-respiring and hot-blooded forms might exist. Hitherto the

highest advancement that animal life could reach was in batrachian and

lizard-like organisms; yet even these were destined to participate in

the change, increasing in magnitude and vital capacity. The pterodactyl

of the chalk, a flying lizard, measures nearly seventeen feet from tip

to tip of its wings. The air had now become suitable for mammals, both

placental and implacental, and for birds. One after another, in their

due order, appeared the highest vertebrates: marine, as the cetacean;

aerial, as the bat; and in the terrestrial, reaching, in the Eocene,

quadrumanous animals, but not, until after the Pliocene, man.

[Sidenote: The date of organisms may change, but the order not.]

Although the advance of geology may hereafter lead to a correction of

some of the conclusions thus attained to respecting the first dates of

different organic forms, and carry them back to more ancient times, it

is scarcely likely that any material modification of their order of

occurrence will ever be made. Birds, mammals, reptiles, fishes, and

invertebrates may each be detected in earlier strata; even in some of

those formations now regarded as non-fossiliferous, organisms may be

found; but it is not at all probable that the preponderance of reptiles

will ever cease to be the essential characteristic of the Secondary

rocks, or that of mammals of the Tertiary, or that a preceding period of

vast duration, in which the type of life had been the invertebrate, will

ever be doubted. Nothing, probably, will ever be discovered to

invalidate the physical conclusion that, while there was an excess of

carbonic acid in the air, the Flora would tend to be Cryptogamic and

Gymnospermic, and that there would be a scarcity of monocotyledons and

dicotyledonous angiosperms in the coal; nothing to disprove the fact

that the animals were slow-breathing and cold-blooded; and that it was

not until after the oxygen of the air had increased and the mean

temperature had declined that birds made their appearance. Though both

placental and marsupial animals may hereafter be found earlier than in

the Stonesfield slate; though wood and herb-eating beetles,

grasshoppers, dragon-flies, and May-flies may be found beneath the lias,

and scorpions and cockroaches beneath the coal, though, also beneath the

coal, salamanders and Sauroid batrachians, of which the archegosaurus is

an example, may occur; though reptiles, as the telerpeton, may be found

deeper than the old red sandstone; yet the connexion between aerial

constitution and form of life will never be shaken. Still will remain

the facts that the geographical distribution of types was anterior to

the appearance of existing species, that organisms first appeared in a

liquid medium, primitively marine, then fluviatile, and at last

terrestrial; that Radiates, Molluscs, Articulates, Vertebrates, were all

at first aquatic, and that the Radiates have ever remained so; that the

plane of greatest vital activity has ever been the sea-level, where the

earth and air touch each other; that the order of individual development

is the order of mundane development. Still will remain the important

conclusions that the mammalian Fauna has diverged more rapidly than the

testaceous; that hot-blooded animals have not had that longevity of

species which has been displayed by the cold, just as we observe in the

individual the possibility of muscular contraction by a given galvanic

force lasts much longer in the latter than in the former; that if the

hot-blooded tribes have thus a briefer duration, they enjoy a

compensation in the greater energy of their life--perhaps this being the

cause and that the effect; that, notwithstanding the countless forms

exhibited by species, their duration is so great that they outlive vast

changes in the topographical configuration of countries--the Fauna of

some countries having been in existence before those countries

themselves; that the plan of individual development has ever been as it

is now, and that sameness of external influence produces similarity of

organization.

[Sidenote: The doctrine of catastrophes and uniformity.] In its early

history theoretical geology presented two schools--one insisting on a

doctrine of catastrophes, one on a doctrine of uniformity. The former

regarded those changes which have manifestly taken place in the history

of our planet as having occurred at epochs abruptly. To this doctrine

the prevailing impression that there had been providential interventions

lent much force. The other school, reposing on the great principle of

the invariability of the laws of Nature, insisted that affairs had

always gone on at the same rate and in the same way as they do now.

Hence it maintained an opposition to the catastrophists, and in this, it

may be said, was actually not true to its own principles. Any doctrine

of uniformity, rightly considered from its most general point of view,

includes an admission of catastrophes. Numerous illustrations of this

truth spontaneously suggest themselves. A tower, the foundations of

which are slowly yielding, may incline more and more for many centuries,

but the day must come in which it will fall at last. In the uniformity

of the disturbance a catastrophe was eventually involved. And thus, in

what has been said respecting geological events, though they are spoken

of as proceeding quietly and with uniformity, it may be understood that

sudden crises are also contemplated. Moreover, those who adopt the

doctrine of uniformity in an absolute sense must pay a due regard to the

variations in intensity of physical acts which their own principles

imply. The uniform cooling of a hot body actually means a cooling at

first fast, and then slower and slower; and invariability of chemical

change actually implies more violent and summary modifications at a high

temperature than at one which is low.

But, though it may at first sight have appeared that an admission of the

doctrine of catastrophes is in harmony with a providential government of

the world, and that the emergence of different organic forms in

successive ages is a manifestation of creative intervention, of which it

was admitted that as many as from twelve to twenty, if no more,

successive instances might be recognized, we may well congratulate

ourselves that those important doctrines rest upon a far more

substantial basis. Rightly considered, the facts lead to a very

different conclusion. [Sidenote: Successive forms assumed by man.]

Physiological investigations have proved that all animals, even man,

during the process of development, pass in succession through a definite

cycle of forms. Starting from a simple cell, form after form, in a

definite order is assumed. In this long line of advance the steps are

ever, in all individuals, the same. But no one would surely suppose that

the changed aspect at any moment presented is due to a providential

interposition. [Sidenote: But they are rigidly determined by law.] On

the contrary, it is the inevitable result of what has been taking place

under the law of development, and the sure precursor of what is about to

follow. In the organic world, the successive orders, and genera, and

species are the counterparts of these temporary embryonic forms of the

individual. Indeed, we may say of those successive geological beings

that they are mere embryos of the latest--embryos that had gained a

power of reproduction. How shall we separate the history of the

individual from the history of the whole? Do not the fortunes and way of

progress of the one follow the fortunes and way of progress of the

other? If, in a transitory manner, these forms are assumed by the

individual, equally in a transitory manner are they assumed by the race.

Nor would it be philosophical to suppose that the management in the one

instance differs from the management in the other. If the one is

demonstrably the issue of a law in action, so must the other be too. It

does not matter that the entire cycle is passed through by the

individual in the course of a few months, while in the race it demands

ages. [Sidenote: Individual and race development conducted in the same

way.] The standard of time that ought to be applied is the respective

duration of life. In man it is much if he attains to threescore years

and ten; but the entire period of human record, embracing several

thousand years, offers not a single instance of the birth, maturity, and

death of a species. They, therefore, who think they find, in the

successive species that have in an orderly manner replaced each other in

the life of the earth, the sure proof of Divine intervention, would do

well to determine at what point the production of such forms by law

ceases, and at what point their production by the immediate act of God

begins. Their task will be as hard to tell where one colour in the

rainbow ends and where the next commences. They will also do well to

remember that, in great mundane events, the scale of time is ample, and

that there may be no essential difference between a course that is run

over in a few days and one that requires for its completion thousands of

centuries.

[Sidenote: Catastrophes disproved by the co-existence of types.] The

co-existence of different types in the organic series was the

incontrovertible fact by which was demonstrated the gradual passage from

form to form without catastrophes, the argument relied upon gathering

strength from such circumstances as these, that even the fossil shells

of the modern Italian tuffs which are not extinct exhibit a slight want

of correspondence when compared with those now inhabiting the

Mediterranean, some of the old ones being twice and a half as large as

the present, and that there is a numerical passage from strata

containing seventy per cent. of recent shells to those that are

altogether recent, or contain one hundred per cent. This is manifestly

indicative of a continually changing impression bringing on a

corresponding modelling. It is the proof of a slow merging into, or of a

measured assumption of, the new form--a transition, for the completion

of which probably a very long time is required. That the existing

reindeer is found in the same fluviatile deposits with an extinct

hippopotamus seemed certainly to prove that there was a condition of

things in which the co-life of those animals was possible in the same

locality, and that, as the physical causes slowly changed, the one might

be eliminated and the other might be left. That the regulating

conditions were altogether physical was obvious from such facts as that

in the bone-caves of Australia all the mammals are marsupial, and in the

pampas of South America they are allied to such forms as are indigenous,

armadilloes, sloths, etc., showing the tokens of lineage or hereditary

transmission. For still more remote times numerous instances of a

similar nature were detected; thus, throughout the whole Secondary

period, the essential characteristic was the wonderful development of

reptile life, while in the Tertiary it was the development of mammals.

But the appearance of mammals had commenced long before that of reptiles

had ceased. Indeed, the latter event is incomplete in our times; for,

though the marine Saurians have been almost entirely removed, the

fluviatile and terrestrial ones maintain themselves, though diminished

both in species and individuals. Now such an overlapping of reptiles and

mammals was altogether irreconcilable with the doctrine of a crisis or

catastrophe, and, in fact, it demonstrated the changing of organisms in

the changing of physical states.

[Sidenote: Cuvier's doctrine of permanence of species.] Cuvier

maintained the doctrine of the permanence of animal species from the

facts that the oldest known do not appear to have undergone any

modification, and that every existing one shows a resistance to change.

If his observations are restricted to periods not exceeding human

history, they may perhaps be maintained, but that duration cannot be

looked upon as more than a moment in the limitless progress we are

considering, and it was in this view that Cuvier's doctrine proved to be

incapable of defence. [Sidenote: Imperfection of evidence in its

support.] What does it signify if our domestic animals show no

variations when compared with the corresponding images depicted on the

hieroglyphic monuments of Egypt, or with the descriptions left by

ancient authors? Evidence of that kind is valueless. Does the geologist

ask of the architect his opinion whether there have ever been upliftings

and down-sinkings of the earth? If he did, would not every structure in

Europe be brought forward as an evidence that nothing of the kind had

ever occurred? A leaning tower, or a church with inclining walls in

Italy, might pass for nothing; the Pyramids would testify that Egypt

itself had never undergone any disturbance--they remain solid on their

bases, undisturbed. But what is the weight of all this when placed in

opposition with the mass of evidence offered by inclined and fractured

strata? And yet such is precisely the proof offered in behalf of the

permanence of animals. The facts with which the zoologist deals, like

those on which the architect depends, are insufficient for the

purpose--they are wanting in extent of time. There have been movements

in the crust of the earth, though every building in the world may be

perpendicular; there have been transformations of organisms, though for

four thousand years there may have been no perceptible change.

[Sidenote: Control of organisms by physical conditions.] If ever there

had been a universal creation of all possible organic forms or

combinations, forthwith vast numbers of them must have disappeared,

every type being eliminated which was not in correspondence with the

external conditions or with the medium in which it was placed. If the

environment or the physical conditions underwent a variation, a

corresponding variation in the forms that could by possibility exist

must ensue, and, from a thorough study of those not eliminated, the

physical conditions might be ascertained; and conversely, from a

thorough knowledge of the physical conditions, the forms that could

escape elimination might be designated. The facts on which Cuvier rested

did not demonstrate what he supposed. His immobility of species was no

consequence of an innate or intrinsic resistance possessed by them, but

merely an illustration that external physical agents had not undergone

any well-marked variation in the time with which he was concerned.

[Sidenote: Nature of variation of physical conditions.] What is here

meant by variation in physical forces or condition is not any intrinsic

change in their nature, but the varied manner in which they may work by

interfering with one another, or experiencing declines of intensity.

From the fact that we may read in the fixed stars, through the

progressive motion of light, the history of a million of past years, we

may be sure that the forces of nature have undergone no intrinsic

change; that light was propagated at the same rate, was capable of

producing the same optical and chemical effects, and varied in its

intensity by distance as it does now; that heat determined corporeal

magnitudes. These are things that in their nature are absolutely

unchangeable. Always, as now, the freezing of water, and its boiling

under a given pressure, must have been the same; there must have been a

thermometric zero of life and an upward limit, no animal process ever

going on below 32 deg. Fahrenheit or above 212 deg. Fahrenheit.

[Sidenote: Effect thereof on organisms.] But out of this invariability

of natural causes variations in their condition of action arise, and it

is these that affect organic forms. Of such forms, some become at length

incapable of maintaining themselves in the slow progress of change;

others acclimatize, or accommodate, or suit themselves thereto by

undergoing modifications, and this was at last discerned to be the true

explanation of extinctions and appearances, events taking place very

slowly in untold periods of time, and rather by imperceptible degrees

than by a sudden catastrophe or crisis.

[Sidenote: Transmutation of species.] The doctrine of the transmutation

of species has met with no little resistance. They who have refused to

receive it as one of the truths of Nature have perhaps not given full

weight to physiological evidence. When they ask, Has any one ever

witnessed such an event as the transmutation of one species into

another? has any experimenter ever accomplished it by artificial means?

they do not take a due account of time. In the Fables it is related that

when the flowers were one evening conversing, "Our gardener," said the

rose to the lily, "will live for ever. I have not seen any change in

him. The tulip, who died yesterday, told me that she had remarked the

same thing; she believed that he must be immortal. I am sure that he

never was born."

[Sidenote: Two modes of action.] Two modes have been presented by which

we may conceive of the influence of physical agents upon organic forms.

Their long persistent action upon the individual may give rise to

modifications, developing one part, stunting another; and such

variations, being transmitted in an hereditary way, may become firmly

fixed at last. Thus a given plant may, in the course of ages, under the

influence of unremittingly acting physical conditions, undergo a

permanent change, and a really new plant arise as soon as, through the

repetitions of successive generations, the modifications have become so

thorough, so profound, as to be capable of transmission with certainty.

Perhaps this is what has taken place with many of our kitchen-garden

plants, of which the special varieties may be propagated by seeds. But

there is another mode by which that result may be reached, even if we

decline the doctrine of St. Augustine, who, in his work "De Civitate

Dei," shows how islands may be peopled with animals by "spontaneous

generation." All organic forms originally spring from a simple cell, the

development of which, as indicated by the final form attained, is

manifestly dependent on the physical conditions it has been exposed to

during its course. If those conditions change, that final form must

change correspondingly; and in this manner, since all organic beings

come from the same starting-point--the same cell, as has been said,

which helplessly submits to whatever impression may be put upon it--the

issue is the same as though a transformation or transmutation had

occurred, since the descendant is not like its ancestors. Such a manner

of considering these changes is in harmony with our best physiological

knowledge, since it does not limit itself to a small portion of the life

of an individual, but embraces its whole cycle or career. For the more

complete examination of this view I may refer to the second chapter of

the second book of my "Physiology."

[Sidenote: Problem of the modification of forms.] But here has arisen

the inquiry, Does the modification of organic forms depend exclusively

on the impressions of external influences, or is it due to a nisus or

force of development residing in the forms themselves?

Whether we consider the entire organic series in its succession, or the

progress of an individual in his development, the orderly course

presented might seem to indicate that the operation is taking place

under a law--an orderly progression being always suggestive of the

operation of law. But a philosophical caution must, however, be here

exercised; for deceptive appearances may lead us into the error of

imputing to such a law, impressed by the Creator on the developing

organism, that which really belongs to external physical conditions,

which, on their part, are following a law of their own. What is here

meant may be illustrated by the facts that occur on the habitable

surface of a planet suffering a gradual decline of heat. [Sidenote:

Three solutions of it.] On such a surface a succession of vegetable

types might make its appearance, and, as these different types emerged

or were eliminated, we might speak of the events as creations and

extinctions, and therefore as the acts of God. Or, in the second place,

we might refer them to an intrinsic force of development imparted to

each germ, which reached in due season its maximum, and then declined

and died out; and, comparing each type with its preceding and succeeding

ones, the interrelation might be suggested to us of the operation of a

controlling law. Or, in the third place, we might look to the external

physical condition--the decline of heat--itself taking place at a

determinate rate under a mathematical law, and drawing in its

consequences the organic variations observed.

Now the first of these explanations in reality means the arbitrary and

unchallengeable will of God, who calls into existence, and extinguishes

according to his sovereign pleasure, whatever he pleases; the orderly

progression we notice becoming an evidence that his volitions are not

erratic, but are according to pure reason. The second implies that there

has been impressed upon every germ a law of continuous organic

variation--it might have been through the arbitrary fiat of God. The

third implies that the successive types owe their appearance and

elimination to a physical influence, which is itself varying under a

strict mathematical necessity; for the law of cooling, which the

circumstances force on our attention, is such a strict mathematical

necessity.

[Sidenote: Their relative probability.] If at this point we balance the

probabilities of these three explanations, we shall perhaps find

ourselves biassed toward the last, as physiologists have been, because

of its rigorous scientific aspect, and should not be surprised to find

it supported by an array of facts depending on the principle that the

appearance of new forms does not observe a certain inevitable order, or

stand in a certain relation to time. From individual development it

might seem as if the advancing procession of an organism is such that

specific forms ever appear in a certain order one after another, and at

certain intervals; but the fallacy of such a conclusion is apparent when

we attend to the orderly procedure of the physical conditions to which

the developing organism is exposed. [Sidenote: Development is in place,

not in time.] The passing through a given form at a given epoch is due

to the relation being to space and its conditions, not to time. And so

in the life of the earth, if development were according to time, we

should have an orderly succession of grades as the earth grew older, and

in all localities, at a given moment, the contemporary organisms would

be similar; but if it were according to space, that rigorous procedure

would not occur; in its stead we should have a broken series, the

affiliation being dependent on the secularly continuous variation of the

physical condition.

Now this was discovered to be the case. For instance, throughout the

northern hemisphere, during the Tertiary period, an extinct placental

Fauna was contemporaneous with an extinct marsupial Fauna in Australia.

If the development was proceeding according to time, by an innate nisus,

and not according to external influences, the types for the same epoch

in the two hemispheres should be the same; if under external influences,

irrespective of time, they should be, as they were found to be,

different.

If true-going clocks, which owe their motion to their own internal

mechanism, were started in all countries of the earth at the same

instant, they would strike their successive hours simultaneously. But

sun-dials, which owe their indications to an exterior cause, would in

different longitudes tell different times, or, when the needful light

was absent, their shadows would altogether fail.

As to the vegetable kingdom, the principles that hold for the animal

again apply. At a very early period, even before the deposit of the

coal, all the distinct forms of vegetable tissue were in existence, and

nothing to prevent, so far as time was concerned, their being united

together all over the world into similar structural combinations. And,

in truth, as the botany of the Coal period proves, there was a far more

extensive sameness than we see at present, simply because the

distribution of heat was more uniform and climates were less marked. But

from this point the diversity of form in climate distribution becomes

more and more conspicuous, though we must descend, perhaps, as late as

the Wealden before we discover any flowering plants, except Gymnosperms,

as Conifers and Cycads. All this is what might be expected on the

doctrine of external influence, but not on the doctrine of an innate and

interior developmental force.

If, at this stage, attention is once again turned to the animal

kingdom, we find our opinion confirmed. The diminution of carbonic

acid in the atmosphere, the deposit of coal in the earth, the

precipitation of carbonate of lime in the sea, the disengagement of an

increased quantity of oxygen in the air, and the reduction of

atmospheric pressure--different effects contemporaneously

occurring--were soon followed by the consequence which they made

possible--the appearance of hot-blooded mammals. [Sidenote: Cold and

hot-blooded animals.] Perhaps those first arising might, like our

hibernates, lead a sluggish existence, with imperfect respiration;

but, as the media improved and the temperature declined, more vigorous

forms of life emerged, though we have probably to descend to the

Tertiary epoch before we meet with birds, which of all animals have

the most energetic respiration, and possess the highest heat.

[Sidenote: The organisms of the sea.] As with the atmosphere, so with

the sea. Variations in its composition must control the organisms it

contains. With its saline constituents its life must change. Before the

sunlight had removed from the atmosphere so much of its carbonic acid,

decomposing it through the agency of plants, the weight of carbonate of

lime held in solution by the highly carbonated water was far greater

than was subsequently possible, and the occurrence of limestone became a

necessary event. With such a disturbance in the composition of the

sea-water, its inhabiting organisms were necessarily disturbed. And so

again, subsequently, when the solar heat began to preponderate on the

surface over the subsiding interior heat, the constitution of the

sea-water, as respects its salinity, was altered through difference of

evaporation in different latitudes, an effect inevitably making a

profound impression on marine animal life.

[Sidenote: Nature of hereditary transmission.] Supported by the facts

that have been mentioned respecting the later fossils of Australia and

Brazil, and their analogy to forms now existing in those countries, much

stress was laid on the hereditary transmission of structure, and hence

the inference was drawn that such examples are of a mixed nature,

depending in part on external agency, in part on an interior

developmental force. From marsupial animals, marsupials will issue; from

placental ones, those that are placental. But here, perhaps, an

illustration drawn from the inorganic kingdom may not be without

interest and use. Two pieces of carbonate of lime may be rolling among

the pebbles at the bottom of a brook, one perpetually splitting into

rhomboids, the other into arragonitic prisms. The fragments differ from

one another not only thus in their crystalline form, but in their

physical qualities, as density and hardness, and in their optical

qualities also. We might say that the calc-spar crystals gave birth to

calc-spar crystals, and the arragonitic to arragonite; we might admit

that there is an interior propensity, an intrinsic tendency to produce

that result, just as we say that there is a tendency in the marsupial to

engender a marsupial; but if, in our illustration, we look for the cause

of that cause, we find it in a physical impression long antecedently

made, that the carbonate of lime, crystallizing at 212 deg. Fahr.,

produces arragonite, and, at a lower temperature, calc-spar; and that the

physical impression thus accomplished, though it may have been thousands

of years ago, was never cast off, but perpetually manifested itself in

all the future history of the two samples. That which we sometimes speak

of as hereditary transmission, and refer to an interior property,

peculiarity, or force, may be nothing more than the manifestation of a

physical impression long antecedently made.

In the last place, the idea of an intrinsic force of development is in

connexion with time and a progression, and only comes into prominence

when we examine a limited portion or number of the things under

consideration. The earth, though very beautiful, is very far from being

perfect. [Sidenote: The broken organic chain.] The plants and animals we

see are only the wrecks of a broken series, an incomplete, and,

therefore, unworthy testimonial of the Almighty power. We should judge

very inadequately of some great author if only here and there a

fragmentary paragraph of his work remained; and so, in the book of

organization, we must combine what is left with what we can recover from

past ages and buried strata before we can rise to a comprehension of the

grand argument, and intelligibly grasp the whole work.

[Sidenote: Enormous age of the earth.] Of that book it is immaterial to

what page we turn. It tells us of effects of such magnitude as imply

prodigiously long periods of time for their accomplishment. Its moments

look to us as if they were eternities. What shall we say when we read in

it that there are fossiliferous rocks which have been slowly raised ten

thousand feet above the level of the sea so lately as since the

commencement of the Tertiary times; that the Purbeck beds of the upper

oolite are in themselves the memorials of an enormous lapse of time;

that, since a forest in a thousand years can scarce produce more than

two or three feet of vegetable soil, each dirt-bed is the work of

hundreds of centuries. What shall we say when it tells us that the delta

of the Mississippi could only be formed in many tens of thousands of

years, and yet that is only as yesterday when compared with the date of

the inland terraces; that the recession of the Falls of Niagara from

Queenstown to the present site consumed thirty thousand years; that if

the depression of the carboniferous strata of Nova Scotia took place at

the rate of four feet in a century, there were demanded 375,000 years

for its completion--such a movement in the upward direction would have

raised Mont Blanc; that it would take as great a river as the

Mississippi two millions of years to convey into the Gulf of Mexico as

much sediment as is found in those strata. Such statements may appear to

us, who with difficulty shake off the absurdities of the patristic

chronology, wild and impossible to be maintained, and yet they are the

conclusions that the most learned and profound geologists draw from

their reading of the Book of Nature.

[Sidenote: Summary as respects the world in time.] Thus, as respects the

age of the earth and her relations in time, we approach the doctrine of

Orientals, who long ago ascertained that the scales of time and of space

correspond to each other. More fortunate than we, they had but one point

of resistance to encounter, but that resistance they met with

dissimulation, and not in an open way. They attempted to conceal the

tendency of their doctrine by allying or affiliating it with detected

errors. According to their national superstition, the earth is supported

on the back of an elephant, and this on a succession of animals, the

last of which is a tortoise. It is not to be supposed that the Brahmans,

who wrote commentaries on the Surya Siddhanta, should for a moment have

accepted these preposterous delusions--that was impossible for such

great geometers; yet led, perhaps, by a wish to do nothing that might

disturb public feeling, they engaged in the hopeless task of showing

that their profound philosophical discoveries were not inconsistent with

the ancient traditions; that a globular and revolving earth might be

sustained on a descending succession of supporting beasts. But they had

the signal advantage over us that those popular traditions conceded to

them that limitless time for which we have had to struggle.

[Sidenote: The life of the universe.] The progression of life on the

surface of our planet is under the guidance of pre-ordained and

resistless law--it is affiliated with material and correspondingly

changing conditions. It suggests that the succession of organic forms

which, in a due series, the earth's surface in the long lapse of time

has presented, is the counterpart of a like progress which other planets

in the solar system exhibit in myriads of years, and leads us to the

conception of the rise, development, and extinction of a multiplicity of

such living forms in other systems--a march of life through the

universe, and its passing away.

[Sidenote: Multiplicity of worlds implies succession of worlds.]

Magnitudes and times, therefore, go parallel with one another. With the

abandonment of the geocentric theory, and of the doctrine of the human

destiny of the universe, have vanished the unworthy hypotheses of the

recent date of creation and the approaching end of all things. In their

stead are substituted more noble ideas. The multiplicity of worlds in

infinite space leads to the conception of a succession of worlds in

infinite time. This existing universe, with all its splendours, had a

beginning, and will have an end; it had its predecessors, and will have

its successors; but its march through all its transformations is under

the control of laws as unchangeable as destiny. As a cloud, which is

composed of myriads of separate and isolated spherules of water, so

minute as to be individually invisible, on a summer's afternoon changes

its aspect and form, disappearing from the sky, and being replaced in

succeeding hours by other clouds of a different aspect and shape, so the

universe, which is a cloud of suns and worlds, changes in the immensity

of time its form and fashion, and that which is contemporary with us is

only an example of countless combinations of a like kind, which in

ancient times have one after another vanished away. In periods yet to

come the endless succession of metamorphoses will still go on, a series

of universes to which there is no end.