who, after the death of the king, stripped the astronomer of all his estates and drove him penniless from the kingdom. For two years he was without a home, but in 1599 found refuge and a pension with Emperor Rudolph II., of Bohemia. Becoming established in Prague, he set up his instruments, and soon students flocked to him again. Among them came the poor youth, Kepler, who soon made himself invaluable to his master. In return, Tycho was kind to Kepler, and together they labored until the former's death in 1601.
With the advent of Kepler (1571-1630) the real problem of gravity together with its solution took definite form. Always a firm believer in the unity and simplicity of the solar system, Kepler rejected the teaching of Tycho Brahé and adopted Copernicus's scheme in toto. Next, he set about bringing order out of the mass of observations ac-