It elevates rather than degrades

of man.

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.

It might moreover appear that the conclusions to which we come, both as respects the position and age of the world, must the position 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.

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 su

per

centric

the world.

preme 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. The Patristic doctrine had been Anthropothat the earth came into existence but little more than five ideas of the beginning thousand years ago, and to this a popular opinion long cur- and end of rent 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 sons 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 illimitable casting a doubt on her recent date, evidence continually becoming more and more cogent. 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

Rise of the

doctrine of

age.

Indications

depending

gressive motion of

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.

The discovery of the progressive motion of light offered the on the pro- means of an absolute demonstration of this connection. 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.

light.

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

tion of the

earth

This astronomical argument, which serves as a general in- Investigatroduction, is strengthened by numerous physical and physio- age of the logical facts. But of the different methods by which the age through the of the earth may be elucidated, I shall prefer that which ap- phenom proaches 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.

of heat.

cal heat

the earth's

As correct astronomical ideas began to prevail, it was per- Astronomiceived that all the heat now on the surface of our planet is de- alone on rived from the sun. Through the circumstance of the inclina- surface. tion 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. This thermometric equilibrium not only holds good for the The equili surface, it may also be demonstrated for the whole mass of the terior heat, planet. The day has not shortened by the of a second since the time of Hipparchus, and therefore the decrease of heat cannot have been so much as the of a Fahrenheit degree, on the hypothesis that the mean dilatation of all terrestrial substances is equal to that of glass, Too 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.

18 00

brium of in

Its ancient

A vast body of evidence has, however, come into prominence, decline.

VOL. II.

U

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 menNecessity of tioned? Simply by the admission that there have elapsed a long time. prodigious, it might almost be said limitless periods. As thus the true state of affairs began to take on a 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 giving conductibility by radiation in a vacuum.

Indications of the inte

the earth.

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.

One fact after another bearing upon the question gradually rior heat of 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° 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 as that the water which rushes up from a depth of 1794 feet in the Artesian well of Grenelle has a temperature of 82° Fahr. The mean temperature of Paris being about