196 NATIONAL ACADEMY OF SCIENCES 
short time, after which he was appointed Superintendent of the 
Nautical Almanac. Not long afterwards, in 1859, he was given 
charge of the mathematical department in the Naval Academy at 
Annapolis, but at the outbreak of the Civil War, he again re- 
sumed the office of Superintendent of the Nautical Almanac in 
Cambridge. During the years in which he was connected with 
this office he made many contributions to mathematics and 
astronomy, the most important of which was his series of tables 
of Mercury. 
In 1866 Professor Winlock was appointed Professor of 
Astronomy in Harvard College and Director of the Harvard 
Observatory.” Here he exerted himself in strengthening the 
equipment of the observatory by the addition of many important 
instruments and aids to astronomical work. The transit circle 
of the observatory, a costly instrument, had proved unsatisfactory, 
and Winlock succeeded in obtaining funds from friends of the 
Observatory to replace it. To arrange for the construction of the 
new instrument, he visited the principal observatories in Europe 
in 1867. He also devised improvements which were afterwards 
adopted by other astronomers. Between 1871 and 1875, 30,000 
observations were made with this instrument, under Winlock’s 
direction. 
In 1869, Professor Winlock was appointed head of a party to 
cooperate with the Coast Survey in observing the total eclipse of 
the sun in Kentucky. On this occasion he succeeded in making 
the first photograph of the solar corona made during any eclipse. 
At the request of the Superintendent of the Coast Survey, he 
organized and led the party sent to Spain to observe the total 
eclipse of the sun occurring on December 22, 1870. During this 
eclipse a telescope of long focus, fixed horizontally, and without 
an eyepiece, which was devised by Winlock for photographic 
work, was used by all the observers. 
Winlock devised many improvements in spectroscopic instru- 
ments, and also in 1872 greatly improved and extended the time- 
° At a later date he also held the position of Professor of Geodesy in the Lawrence and 
Mining Schools of Harvard College. 
