AT THE ROYAL OBSERVATORY, CAPE OP GOOD HOPE. 465 



telescope, the mean of several nights' observations, under similar circumstances, will not be 

 wide of the truth. 



" The only inconvenience of the Munich mounting, as respects this instrument and form of 

 pillar, is when stars near f) Hydri are observed, telescope west. The projection of the parts 

 about the driving clock stops the telescope in the meridian. Elsewhere, objects can be followed 

 15 or 20 minutes across the meridian without reversion, uninterrupted by the pier. 



" When describing the dome I omitted to mention, that by means of a system of pins and 

 projecting cogs from the upper curb, the dome is moved with great facility, either by a lever or 

 pulley. A cord and pulley are made use of in the continued observation of the same object. 



' The situation of the building is 53 yards distant from the nearest corner of the west wing 

 of the observatory. The instrument commands the sweep of the horizon, excepting the angle 

 cut off by the observatory to the southeast, viz: between 320 and 350 in azimuth, reckoned from 

 the south point round by the west. 



" In conclusion, it may not be out of place to mention that almost the first pointing of the 

 telescope proved the rapid motion of the binary v Coronce Australia, in position and distance, 

 predicted by Sir JOHN HERSCHEL from very scanty data." 



The proof-sheets of Mr. Maclear's observations have been read by myself with his original 

 MS., and every attention given to insure accuracy. 



j. M. a. 



WASHINGTON, 1855. 



59 



