136 NATIONAL ACADEMY OF SCIENCES 
able to remain there only a year on account of a serious affection 
of the eyes, brought on by overstudy. In 1836 he was assigned 
to the Depot of Charts and Instruments, an office whose function 
was in part the rating of chronometers. Gilliss was soon placed 
in charge of this office and began to make observations for the 
determinations of time. In the winter of 1837-8 he observed 
a large series of transits of the moon and moon-culminating 
stars. When the United States Exploring Expedition sailed in 
1838, Gilliss remained in Washington under orders to observe 
moon-culminations, occultations and transits, and continued in 
that work during the four years in which the expedition was 
absent. He published the first American volume of astronomical 
observations, prepared the first catalogue of stars and con- 
structed a working astronomical observatory. At the same time 
he carried on magnetic and meteorological observations. 
Gilliss pursued his investigations with remarkable energy and 
studious application and was possessed of extraordinary powers 
of sight which enabled him to make extremely accurate obser- 
vations. 
The establishment of the U. S. Naval Observatory in 1842 
was brought about largely through the efforts of Gilliss, and he 
was charged with the preparation of the plans for the construc- 
tion of the building and the arrangement of the instruments. 
In 1846 he was assigned to duty in the Coast Survey under 
Professor Bache. 
At the suggestion of Dr. Gerling of Marburg, he initiated a 
movement for an expedition to Chile, for the purpose of ob- 
serving the planet Venus and in 1849 established a station at 
Santiago where for nearly three years he carried on observations 
of Venus and Mars, together with meridian observations of 
2,000 stars and also zones of about 23,000 stars, as well as obser- 
vations on earthquakes, and barometer and thermometer readings. 
From 1852 to 1856 he was occupied in preparing the report 
of this expedition which comprises six quarto volumes. In 1858 
he made a brief expedition to Peru and in 1860 to Washington 
Territory for the purpose of observing the total eclipse of the 
