September, 1846. The next year, a satellite of Neptune, as the new planet has been named, was discovered by Mr. Lassell, of Maidenhead, England.

From this hasty survey of the Solar System, as delineated by Professor Newcomb, it is evident that so great advances have been made by astronomy, that the facts and figures of even twenty-five years ago are no longer quotable, unless newly verified. This state of things is nothing new. The march of intelligence is steady and remorseless. Dreams are dissipated, errors fall, and knowledge grows. The day advances, and things which put on one appearance in the twilight wear another at sunrise. One great duty of the scientists of every age is to correct the mistakes of those who preceded them, and to do it modestly, in the full persuasion that their own work will be as mercilessly revised by those who come after them. In science the classic myth of Saturn's devouring his children must be reversed. The newborn ages devour their progeni

tors.

Our author treats of comets, meteors and shooting stars, in a manner which is not only interesting, but as thorough as the proposed size of the volume admits. One new phenomenon may here be cited in proof of the fact that the celestial enginery is not the changeless thing that some imagine it. Biela's comet, which was seen in 1772, and which was observed from time to time for eighty years, as it returned at intervals of a little less than seven years, separated into two parts in January, 1846. These were seen again in 1852, more widely separated than before, but have never been seen since, unless, as is argued with some show of proof, some of its fragments floated across the path of the Earth, and produced the meteoric shower which occurred on the night of November 27, 1872.

Part fourth discusses the stellar universe, and is so full of marvels that we know not how to select from its richness. The theories of Kant and Herschel are described, in regard to the way in which the universe was formed. The author also treats of the number of the stars, the constellations, new and variable stars, double stars, binary systems, clusters of stars, nebulæ, and the motions of the stars. "The representation which we give in Figure 104 is from a drawing made by Mr. Trouvelot with the great Washington telescope. In

brilliancy and variety of detail" the great nebula of Orion "exceeds any nebula visible in the Northern Hemisphere."Page 447.

It is added that the spectroscope shows the lines which indicate burning hydrogen, and, perhaps, nitrogen, and, therefore, there is "a certain probability" that this nebula is a mixture of these gases. Without any pretense of being as able to judge of these things as Professor Newcomb, we feel free to say that the gas theory, on his own methods of reasoning, seems to have a very slight foundation. The reader will remember that Herschel's theory that the light and heat came to us, not from the body of the sun itself, but from an atmosphere of fiery vapors surrounding it, while the central mass may be relatively dark and cool, was condemned on the ground that no such atmosphere could send forth, from age to age, without perceptible diminution, such floods of light and heat. How, then, can a mere cloud of hydrogen, immeasurably more distant than the sun, shine on us, from age to age, with undimmed radiance? What keeps it in an incandescent state? Above all, how can a mass of mere vapor, subject to no

forces but such as the component floating atoms exert upon each other, maintain unchanged the very peculiar shape which this nebula bears?

The question, Do the stars really form a system? is discussed, and answered, on probable grounds, in the negative. Motions are detected in some of what have been called the fixed stars, but no such motions as indicate a common center, or a unity of organization. Here and there a star is known to change its place in the distant heavens, though it requires the skillful use of the best instruments to estimate its motion; but it seems to be wandering alone, as if the rest of the universe had no existence. Consequently the idea of the great central Sun, around which at least our Sun and all the stars visible to the unaided vision perform their vast revolutions, fades into thin air, with a great many other brilliant dreams.

But while this noble science is the field in which the human intellect has performed some of its grandest achievements, its mighty task is only begun. Five centuries ago, when the geographers of the times sat down to make a map of Europe, they marked out its empires and kingdoms, and drew the line of its western coast, with its capes, and bays, and islands along the shore; but still farther Westward lay a wide wilderness of waters, which they had never explored, and of which they knew nothing. They, therefore, shaded off the lines which indicated the ocean, and on the blank spaces beyond wrote honest and significant words, Mare Tenebrosum, the Dark Sea. Thus, with all the light of our age, after all the triumphs that science has won, there still rolls around us, on every side, the great deep of the unknown; and though adventurous navigators are launching forth upon it, and discovering new islands, and even broad continents, of knowledge, we shall never cast anchor at the farther shore.

Another important point may properly be mentioned in this connection: the bearing of modern scientific discovery upon revealed truth. Our author does not introduce this question. His work is on astronomy, not religion. It is the province of the scientist to push his inquiries in every direction. He is justified in looking for a physical cause for every physical effect, and in tracing the succession backward just as far as he feels solid ground under his feet. We have no fears. FOURTH SERIES, VOL. XXXI.-18

that discovered truth will ever conflict with revealed truth. The multiplication table will never refute conic sections. The intelligent Christian believer hears with unalloyed pleasure of the brilliant discoveries of our age, and cherishes the hope of still greater advances in coming years.

There has never been a conflict between true science and true religion. There have, indeed, been collisions between scientists and ecclesiastics; but this does not prove the charge. The collisions of scientists among themselves have been far more numerous and far more bitter. When Galileo published his discovery of the moons of Jupiter, there was at first a general expression of incredulity; and one astronomer refused to look through the telescope, lest he should see and be convinced. Men become famous for their acquaintance with the science of their times; and when some advance is made which calls upon them to retract, and reconstruct, and become learners again, they are slow to surrender their honors.

It is said that when Harvey, in 1628, published his discovery of the circulation of the blood, no physician forty years old at that time ever believed it. The professors in the medical colleges of the Continent attacked him, and in London ítself, notwithstanding court favor, his professional practice declined. When Jenner, in 1796, introduced vaccination as a preventive of small-pox, he was treated with derision; a medical society with which he was connected threatened to expel him; and the medical profession generally, both in England and the United States, vigorously resisted all attempts to introduce the "diabolical" device.

Professor Newcomb nowhere directly avows his belief in the Hebrew Scriptures, but he takes positions which can in nowise be reconciled with atheism. The idea that the whole Solar System once existed as an immense volume of glowing gas, and became what we find it by a process which occupied a million ages, is not irreconcilable with the first two verses of Genesis. If it can be shown that the germs of the various forms of life now existing were gradually evolved by forces working in the primordial atoms, the next twenty verses do not deny it. And the idea that the Creator made the worlds by gradual process, first calling into being the glowing mass of vapor, and clothing its myriad atoms with all the possibilities of the com

pleted work, is really an exalted conception of His boundless. intelligence and infinite power.

We count these evolution theories "the stuff that dreams are made of;" but, whether verities or dreams, they are logically theistic. To be eternal, things must be changeless. If the visible creation is the product of lengthened processes, it surely had a beginning. Prove any sort of process which advances by successive stages, and you prove a beginner as well as a beginning. The teachings of science are very significant in another direction; they assure us that, left to itself, and as controlled by the laws of matter only, the whole visible universe must come to an end.

All modern science seems to point to the finite duration of our system in its present form, and to carry us back to the time when neither Sun nor planet existed, save as a mass of glowing gas. How far back that was it cannot tell us with certainty; it can only say the period is counted by millions of years, but, probably, not by hundreds of millions. It also points forward to the time when Sun and stars shall fade away, and nature shall be enshrouded in darkness and death, unless some power now unseen shall uphold or restore her.-Page 489.

The progressive change exhibited by the operations of nature consists in a constant transformation of motion into heat, and the constant loss of that heat by radiation. As Sir William Thompson has expressed it, a constant "dissipation of energy" is going on in nature. We all know that the Sun has been radiating heat into space during the whole course of his existence. . . But it is now known that heat cannot be produced except by the expenditure of force, actual or potential, in some of its forms; it is, also, known that the available supply of force is necessarily limited.. Hence, this radiation cannot go on forever unless the force expended in producing the heat be returned to the Sun in some form. That it is not now so returned we may regard as morally certain.-P. 500.

That which approaches an end must certainly have had a beginning. If it had existed from all eternity, then the processes which bring it to an end would have been completed, and the end reached, a whole eternity ago. We have, then, as the result of the boldest research, and the severest logic of modern science, the conclusion that the visible universe had a beginning, and, unless sustained by a power above itself, must end in universal darkness and death. Spencer himself admits that nature tends to universal equilibrium, and that universal equilibrium is the cessation of light and heat, and all the