surpassed in size by only two other refractors in the world, 
each of which was 15 inches in diameter, and one of them 
was at Harvard College. In 1865 the observatory became 
the possession of the university, with a modest endowment 
fund, and Prof. Samuel Pierpont Langley was made director, 
continuing 20 years. 
Langley’s skill as a draftsman and illustrator enabled 
him to make the finest drawings of sunspots ever executed. 
At that time, visual observations were the only means of the 
study of the sun. The photographic plate has since super- 
seded the eye, aided by many modern instruments, including 
the spectograph and spectroheliograph: but Langley’s visual 
observations, made in Pittsburgh, are now regarded as 
classic. He not only studied the solar spectrum visually, but 
he also used a very delicate thermo instrument called the 
bolometer, extending human knowledge of the spectrum far 
into the infra-red, much beyond the power of the eye to see. 
This region of the spectrum mapped by him is that part from 
which the earth gets most of its heat energy, affecting the 
thermometer, but not the eye. 
While at the Allegheny Observatory, Langley made his 
experiments on the lifting power of the air by means of a 
whirling table on which were mounted planes tilted at various 
angles—the precursors of the wings of the airplane. Langley 
himself constructed the first airplane after he left Pittsburgh 
and went to Washington as secretary of the Smithsonian 
Institution. The failure of his plane to make a flight greatly 
distressed him. He had the right idea, however, and its lack 
of success was not due to the plane itself, but to the failure of 
the launching apparatus, which, instead of directing the 
plain upward, threw it downward into the Potomac River. 
Much ridicule was heaped upon Langley for his attempt at 
air flight, and he found it impossible to obtain the necessary 
funds to continue his experiments. However, this same 
machine, in the hands of the Wright Brothers, made a suc- 
cessful flight, long after the death of Langley, proving that 
he was the inventor of the airplane. James E. Keeler was 
another director who did excellent work. His principal 
achievement was the spectroscopic proof of the constitution 
of Saturn’s rings, by a spectrograph of his own design.