SANTIAGO OBSERVATIONS. 

 Longitude from occupations. 



li 



Making each result from occultation equivalent to two from moon culminations, and then 

 combining the partial determinations by the two methods with weights proportioned to their 

 respective numbers, we have for the adopted longitude of Santiago west of Greenwich 



4 h 42 m 33-.81. 



DIFFERENTIAL OBSERVATIONS. 



MODE OF OBSERVING. 



A siderial chronometer was used in the differential observations. It was compared with the 

 clock immediately before or after the series, though more frequently after the series for the 

 evening was completed. 



When the lamps were lighted, and the amount of illumination properly diminished, the 

 telescope was directed approximately to the place of the planet, its declination circle clamped, 

 and the relative place of the proper comparing star ascertained by inspection of the map and 

 ephemeris. The instrument was then moved by the slow motion screws so that each object 

 should pass equidistant from the centre of the field. Moving the micrometer screw so that its 

 wire would nearly coincide with the object first in right ascension, the telescope was then turned 

 to the west by the tangent screw to the hour circle until the first object to be observed was just 

 without the field. It remained immoveable in this position until the transits and difference of 

 declination of the two had been recorded, after which, it was again thrown to the west, and so 



