the frontispiece of an immortal code; who shall be able to exclaim in dithyrambic language, and without incurring the reproach of anyone, 'The die is cast; I have written my book; it will be read either in the present age or by posterity, it matters not which; it may well await a reader, since God has waited six thousand years for an interpreter of his words.'-Arago.

The philosophical significance of Kepler's discoveries was not recognized by the ecclesiastical party at first. It is chiefly this, that they constitute a most important step to the establishment of the doctrine of the government of the world by law. But it was impossible to receive these laws without seeking for their cause. The result to which that search eventually conducted not only explained their origin, but also showed that, as laws, they must, in the necessity of nature, exist. It may be truly said that the mathematical exposition of their origin constitutes the most splendid monument of the intellectual power of man. - Draper.

GALILEO.- Columbus discovered America when Copernicus was but 19, and before the birth of Tycho Brahe, Magellan had completed the proof of the earth's rotundity by actually sailing around it, while Luther had stirred up the great religious revolt of Protestantism. The later years of Kepler and Galileo fell within the period of the Thirty Years' War, of which neither was to witness the close. Permanent English settlements in America had just begun. Galileo (1564-1642), born on the day of Michael Angelo's death, "nature seeming to signify thereby the passing of the sceptre from art to science," and in the same year with Shakespeare, exerted a mighty influence on the development of science in many fields, and in particular laid the foundations of modern dynamics.

It is a remarkable circumstance in the history of science that astronomy should have been cultivated at the same time by three such distinguished men as Tycho, Kepler and Galileo. While Tycho in the 54th year of his age was observing the heavens at Prague, Kepler, only 30 years old, was applying his wild genius to the determination of the orbit of Mars, and Galileo, at the age of 36, was about to direct the telescope to the unexplored regions of space. The diversity of gifts which Providence assigned to these three philosophers was no

less remarkable. Tycho was destined to lay the foundation of modern astronomy by a vast series of accurate observations made with the largest and the finest instruments; it was the proud lot of Kepler to deduce the laws of the planetary orbits from the observations of his predecessors; while Galileo enjoyed the more dazzling honor of discovering by the telescope new celestial bodies and new systems of worlds. Brewster.

Coming into a world still dominated by the Aristotelian tradition, Galileo is puzzled by the conflict between his own observations and the accepted theories, but firm and fearless in his convictions, he eagerly and powerfully controverts the older notions, incidentally gaining enemies as well as disciples. What those accepted theories were may be exemplified by the following passages from a work of Daniel Schwenter (1585-1636), professor of mathematics at Altdorf:

'When a body falls it moves faster the nearer it approaches the earth. The farther it falls the more power it possesses. For everything which is heavy, hastens according to the opinion of philosophers towards its natural place, that is the centre of the earth, just as man returning to his fatherland becomes the more eager the nearer he comes, and therefore hastens so much the more. Still another natural cause contributes to this. The air which is parted by the falling ball, hastens together again behind the ball and drives it always harder.'

If the Copernican theory were true, the bullet remaining two minutes in the air would be left many miles behind by the revolving earth, a distance which the moving atmosphere could not possibly carry it. The rainbow is "a mirror in which the human understanding can behold its ignorance in broad day." The powder drives the bullet in an oblique line to the highest point of its path, then follows motion in an arc, finally, the natural motion vertically downward.

In his whole point of view and habit of mind Galileo embodied the attitude and spirit of modern science. He was keenly alert in observing, analyzing, and reflecting on natural phenomena, eager and convincing in his expositions, sceptical and intolerant

of mere authority, whether in science, philosophy, or theology. It was a true instinct of the conservatives to recognize in him the champion of a principle fatally hostile to their own. Between these antagonistic principles no permanent peace was possible.

While still a mere youth, he discovered the regularity of pendulum vibrations by observing the slow swinging of the cathedral lamp of Pisa (1582). Before he was 25 he published work on the hydrostatic balance (1586), and on the centre of gravity of solids. Only a little later he conducted at the leaning tower simple experiments in falling bodies, which upset world-old notions on this everyday matter, showing that the velocity of descent is not, as was commonly supposed, proportional to weight. And "yet the Aristotelians, who with their own eyes saw the unequal weights strike the ground at the same instant, ascribed the effect to some unknown cause, and preferred the decision of their master to that of nature herself.”

He further showed that the hypothesis of uniform acceleration accounted correctly for the observed relations between space, time and velocity, and that the path of a projectile is a parabola. In the words of a recent authority, when Galileo

deduced by experiment, and described with mathematical precision, the acceleration of a falling body, he probably contributed more to the physical sciences than all the philosophers who had preceded him.

Hearing of the telescope newly invented in Holland, he constructed one for himself, by means of which he discovered sun spots, the mountains of the moon, the satellites of Jupiter, the rings of Saturn, and the phases of Venus. The sensation created by these discoveries is described in the following passages from Fahie's Life of Galileo and Brewster's Martyrs of Science.

'As the news had reached Venice that I had made such an instrument, six days ago I was summoned before their Highnesses, the Signoria, and exhibited it to them, to the astonishment of the whole senate. Many of the nobles and senators, although of a great age, mounted more than once to the top of the highest church tower in