cends from hill to hill, from mountain top to mountain top, till not a summit interrupts his vision from border to border of the physical universe.

In this grand result of added knowledge on the one hand, and of increased circumference and sublimity of human conceptions on the other, no science has equalled astronomy. Many of the discoveries made in consequence of astronomical observations I have already enumerated. There is, however, another extensive group of discoveries which were even more directly the consequences of astronomical inquiries.

These are the instruments, the means, and the mathematical analysis by which the problems of the celestial phenomena were solved. Before the time of Galileo, the means of observing the heavenly bodies. were scarcely better than the smoked glass used by boys to look at eclipses. One of the greatest discoveries in mechanical knowledge produced by astronomy was that of the telescope. In the hands of Galileo, and while yet in its rude state, the surface of the moon, the forms of the planets and their satellites, were perfectly observed. Then commenced the unfolding of that vast field of starry orbs which has continued its development from Galileo to Herschel, and from Herschel to Struve and Rosse. The telescope was followed by the microscope, the pendulum clock, and various other mechanical inventions applied to astronomy. Step by step the mechanics of science were enlarged and improved by that very

theoretical research whose inquiries they were destined to aid and advance.

Then came the discovery of the composition of light, of which it has been aptly said, that "Newton untwisted all the shining robe of day, and made known the texture of that magic garment which the God of nature has kindly spread over the surface of the visible world."* Great as were his other discoveries—his decomposition and recomposition of light remains the most brilliant gem in the earthly crown of Newton.

Beautiful and almost incomparable as these visions into the mysteries of nature were, abstract mathematics considered in regard to itself was to receive a greater than either. This was the introduction of the geometry of infinites; the mathematical analysis now known as the Calculus, or Fluxions. This is the Infinitesimal Analysis, and is that peculiar calculation which determines the laws of curve lines. It was the instrument invented by Newton, previous to his astronomical demonstrations, and used by him, La Place, and others, in calculating to their utmost limits the powers and forces involved in the mechanics of the planetary system. Then the domain of mathematical science was extended in every direction. Professor Playfair said that "these problems are connected with the highest attainments of wisdom, and the greatest exertions of power. They seem like so

* Playfair's Discourse.

many immovable columns erected in the infinity of space, to mark the eternal boundary which separates the regions of possibility and impossibility from one another."

Such were some of the additions to knowledge made in the search after the mere means and instruments by which the astronomer should ascend the stairway of the visible creation, enter the midst of its mechanical machinery, and direct the chariot of science through the throng of revolving worlds!

But these newly discovered elements of knowledge -various, beautiful, and wonderful as they are-were but a part, and the smallest part, of the effects produced upon the human mind by the pursuit of astronomy. Beattie, in his Essay on Truth, says, that the mind partakes of the character of the natural scenery by which it is surrounded. The mountaineer is the child of liberty; and virtue dwells amidst the pure air of his lofty hills. If such be the effect of natural scenery on the surface of the earth, what must be the sublime conceptions of him who, even in imagination, passes behind this earthly atmosphere, ascends the beams of the evening star, reaches the zenith of the firmament

riding sublime

Upon the seraph wings of ecstasy,
The secrets of the skies to spy!"

It was a sublime idea to conceive the infinitesimal It was a vision, exceeding all the bounds

analysis.

of poetry, to take the rainbow colors from the white light of the sun, to recompose them again, and make their colors resume the transparent beams whence they were taken; but these were inferior acts in the drama of science, to that which finally solved the problem of the planetary system, and which accounted for all its movements, its relations, its irregularities, and its phenomena.

THE PROBLEM OF THE CELESTIAL BODIES.

In order to know what the human mind has accomplished in this respect, we must state, and understand, if possible, the exact problem which was presented for its solution in the phenomena of the celestial bodies. It involves no technical terms, but may be understood by a statement of common facts, and of what reason obviously requires to solve those facts.

In the sixteenth century, the era of Tycho Brahe, the celestial phenomena to be accounted for were these:—it was known the earth was a globe, and hung in indefinite space; it was known that in the firmament around it were innumerable other globes of light they too were hung in indefinite space. Between all these globes, or between any two of them, there was no communication. Some appeared to be in motion, and some appeared to be stationary. Man was placed on the surface of one of this host of

globes; the only element common to him with them, was light-the only fact in their constitution which could be observed, was motion. Even this motion deceived him, for its appearance was often contrary to its reality.

These were the facts, and no other aid was to be had than what reason could furnish. These distant bodies were intangible to human hands, unapproachable by any means of conveyance, immeasurable by any instrument. There was no matter in their composition to be analyzed; no airy vessel which should carry tidings, like electro-magnetism, on the wings of thought. The mind alone was to furnish all that could hereafter be known of these unknown worlds. It was a draft on the immortal spirit, to go where only spirits could go!

The problem which these facts required man to solve, if it could be solved, was this :

1. That he should invent and use such mechanical instruments as would observe the minute motions of these distant bodies, and measure accurately the element of time or the relations of motions, the only one which could be calculated.

2. Next, it was required that he should calculate from these relative motions observed in space, the figures, or trace, which these bodies made in the fir

mament.

3. Thirdly, it was required that he should discover and demonstrate the laws of that motion by which a body in space would describe that figure; and that