Astronomy in Gehnani/jfor 1818. 93 



volume of Bessel's publication. The places finally obtained 

 ag-ree very nearly with a catalogue deduced from a smaller 

 number of observations by Bessel himself, which he has lately 

 ^ent over to this country. The most probable error, according to 

 Professor Littrow's calculation, never amounts to the hundredth 

 of a second of time ; the correction of Bessel's former determi- 

 nation never to ^ '. 



II. An Attempt to determine the most probable Orbit of the 

 Comet of 1680. 



A very elaborate essay, continued to the next Number. The 

 author remarks that the whole of Flamsteed and Newton's obser- 

 vations may be represented without an error of more than about 

 20" of space; and he has rejected those of many other persons, 

 which exhibited errors of from 5' to 10'. The period is supposed 

 to be 1589,2 Julian years. 



III. Bohnenberger on a Problem in Practical Geometry. 



A convenient mode of finding, upon a plain table, a point from 

 which three other points subtend given angles. 



V. September awfZ October. 



IV. Continuation of the Essay on the Comet. 



From a very lal)orious investigation of all the observations, and 

 a comparison of their probable values ; the corrected period is 

 found 8814 Julian years, the greatest probable limits of its un- 

 certainty being 6179 and 14030. The mean error of the obser- 

 vations is only half as great on this hypothesis, as upon Halley's, 

 of a period of about 575 years ; and as Bessel has observed, the 

 very circumstance of the accuracy of the recurrence at three suc- 

 cessive periods of 575 years, is of itself an improbability, since 

 the planetary perturbations must, in general, have altered the 

 period from time to time as much as four or five years. 



V. Secjuel of Piazzi's Life. 

 Piazzi was born 19lh March, 174G. The principal events of 



