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 i860 to Washington 

 Territory for the purpose of observing the total eclipse of the 



