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reeled a circle, ten feet in diameter, to be made for this ob- 

 servatory. Mr. Ramsden protracted for many years the exe- 

 cution of the instrument. After beginning one of 10 feet 

 diameter, he afterwards rejected it for one of 9 feet, which 

 was actually divided. The latter he also rejected, and at his 

 death he left unfinished our present instrument of 8 feet dia- 

 meter. This was finished by his successor, Mr. Berge, and 

 placed in the observatory, about the middle of 1808. The 

 long period which elapsed, while the instrument was ex- 

 pected, will be always a subject of regret to myself. On 

 some future occasion I may, perhaps, lay a detailed account 

 of this instrument before the Academy. At present I shall 

 on-ly mention such particulars, as may be necessary to render 

 intelligible the method of making observations with it, and 

 the degree of accuracy to be expected from it. 



The circle is supported in a frame, which frame turns on a 

 vertical axis. The upper part of the frame is of cast iron, 

 turns in a collar, and is connected with the lower part of the 

 frame by four hollow brass cylindrical pillars. The lower part 

 of the frame, which is also of cast iron, terminates in a pivot 

 of steel, which turns in a socket of bell-metal. This socket is 

 moveable south and north, by one screw, and east and west, 

 by another, for the purpose of adjusting the vertical axis. 



The axis cf the circle, a double cone four feet in length, 

 is supported an Ys which are themselves supported by strong 

 bars of brass attached to the cylindrical pillars. The pres- 

 sure of the weight of the circle and its axis is relieved by an 



