57 
larger dimensions, lent the office by the Coast Survey. This 
instrument was made by Troughton, and had a clear aper- 
ture of 33, with a focal length of 63 inches. 
In a very short time after the arrival of Gilliss in Wash- 
ington, he was placed in full charge of this establishment, 
and here he made his first astronomical observations, these 
his being at first solely for determining time, like all those of 
predecessors. A year later, during the winter of 1837-38, 
he observed an extensive series of transits of the moon and 
moon-culminating stars for the determination of longitudes in 
connection with a survey of Savannah River ; but these ob- 
servations appear never to have been reduced. 
At this time he was married to Miss Rebecca Roberts, the 
daughter of John Roberts, Esq., of Alexandria, D. C., with 
whom he passed a life of uninterrupted domestic happiness. 
For more than twenty-seven years, his interests and cares 
and aims were hers ; and he owed much to her encouragement 
and sympathy in his intellectual as well as his domestic life. 
In 1838 the exploring expedition sailed under the com- 
mand of Capt. Wilkes, and for the purpose of determining ~ 
differences of longitude by means of moon-culminations, oc- 
cultations, and eclipses. Special instructions were drawn up 
by him for the observations of these phenomena, and applica- 
tion was specially made by him to the department that Lieut. 
Gilliss “should not be permitted” to leave the depot during 
the absence of the expedition. The late Mr. W. C. Bond, 
who had a transit-instrament mounted at his house in Dor- 
chester, was also engaged for the same purpose, the instruc- 
tions to him and - —_— _— sees These instruc- 
tions al t ti meteorologi 
observations, ond he availed inion of this opportunity to 
procure a portable 3}-inch achromatic, equatorially mounted, 
a variation-transit for use in measuring the magnetic declina- 
