ASTRONOMICAL EXPEDITION TO CHILI. 297 



that measures could be continued long after day-light, 

 if the comparing star was as bright as the seventh mag- 

 nitude. During the second period of Venus in 1852, it 

 was possible to make differential measures only on nine 

 evenings prior to the conjunction, and on eighteen 

 mornings subsequent to .it. There was not a single 

 occasion when the measures were wholly satisfactory. 



As the preceding observations occupied only a part 

 of the time spent in Chili, Lieutenant Gilliss devoted a 

 portion of the intermediate intervals to constructing a 

 catalogue of stars between the south pole and 65 of 

 south decimation. Beginning within 5 of the south 

 pole, a systematic sweep of the heavens was commenced 

 in zones or belts 24' wide. "Working steadily toward 

 the zenith on successive nights, until compelled to re- 

 turn below again to connect in right ascension, the place 

 of every celestial body that passed across the field of the 

 telescope, to stars of the tenth magnitude, was carefully 

 noted down. The space immediately surrounding the 

 south pole was swept in one belt of 5 by moving the 

 circle. Above the polar belt, forty-eight other belts were 

 observed, making in all 24 12' of declination, within 

 which were obtained 33,600 observations of some 23,000 

 stars; more than 20,000 of them never previously 

 tabulated. 



"While astronomical observations received the principal 

 attention, magnetism and meteorology were not neglected. 

 The meteorological instruments were observed tri-hourly 

 during nearly three years, and one day of each month 



13* 



