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mechanical flight, now recognized as having formed the basis for present day success in this field.

After Langley had been called to the secretaryship of the Smithsonian Institution at Washington, he was succeeded at Allegheny by his former assistant, James Edward Keeler. His short directorship was marked by the brilliant proof of the meteoric composition of Saturn's rings, one of the best planned and most striking observations of modern astronomy. Keeler persistently urged the necessity of removing the observatory from its original site, upon which the rapidly growing city had by this time seriously encroached. Steps to bring about this removal were under way, but they were temporarily halted in 1898, when Keeler was called to the directorship of the Lick Observatory. But shortly afterwards these efforts were vigorously renewed by Dr. John A. Brashear, who lias been chairman of the observatory committee since 1894. The new observatory as it stands to-day is in large measure a tribute to the respect and affection in which Dr. Brashear is held by the people of Pittsburgh.

The plans for the new observatory and its equipment are due to Keeler's immediate successor, Professor F. L. O. Wadsworth. and to the present director, Dr. Frank Schlesinger. The principal instruments are the old 13 inch refracting telescope, a 30-inch reflecting telescope (a memorial to Keeler), and a 30-inch refracting telescope (a memorial to William Thaw and his son. William Thaw, Jr.). The last of these telescopes is not quite complete, as the objective remains to be supplied.