ASTRONOMICAL EXPEDITION TO CHILI. 295 



servatory in Chili, were prepared in Washington, and 

 shipped to Valparaiso in the summer of 1849. 



The principal astronomical instruments furnished for 

 the expedition were two telescopes, equatorially mounted, 

 a meridian circle, a clock, and three chronometers. 



The larger telescope was an eight and a half feet 

 refractor, having an object-glass by Fitz, of New York, 

 that afforded a clear aperture of six inches and a half. 

 It was fitted with clock-work by Wm. Young, of Phila- 

 delphia, and by him provided with a micrometer adapted 

 both for differential measurements, and for measurements 

 of position and distance. 



The other telescope was a five feet achromatic, by 

 Fraunhofer. It was also equatorially mounted, and fitted 

 with a micrometer by Young, of Philadelphia. 



The meridian circle was by Pistor and Martins, of 

 Berlin. The object-glass of the telescope had a clear 

 aperture of four and one-third inches, with a focal length 

 of six feet. The circles were thirty-six inches in 

 diameter, both divided to 2', and read by two mi- 

 crometer microscopes, each to a half second. 



The series of astronomical . observations, especially 

 contemplated, consisted of differential measurements 

 during portions of the years 1849, 1850, 1851, and 

 1852, upon Venus and Mars, with stars conveniently 

 situated in the neighborhood of their paths. The ob- 

 servations of Venus chiefly depended upon, were ob- 

 servations near the inferior conjunctions of 1850 and 

 1852. The principal observations of Mars were near 



