60 Notice respecting a new Comet ^ 



The longitude of the ascending node is calculated from th« 

 mean place of the eqmnoctial point on the 1st Jan. 1815 ; and 

 the inclination relates to the plane of the ecliptic at the same 

 time. In this determination tlie perturbations derived from the 

 action of the planets, during the time that tlie comet remained 

 visible, have been taken into the calculation ; and it is derived 

 from a comparison of nearly 200 observation'^. According to the 

 doctrine of chances, it is probable that the error of the time of 

 revolution does not exceed + -27657 of a year, or about 101 

 days. 



The indefatisrable Besscl has also calculated the perturbations 

 which this comet will undergo before its next return. Accord- 

 ing to its regular elements it ought to come again to the perihe- 

 lion on the 14t!i May ISSf); but, on account of the perturba- 

 tions, this event will take place 824 51 days earlier, that is, on 

 the 9ih February 1SS7 ; consequently our successors may expect 

 its return three or four moiiths before or after the 9th February 

 18S7. 



If this comet should have been accurately observed in En- 

 gland, you will much oblige me by sending me the particulars of 

 t!ie observations. In France it has net been dune with' much 

 precision; and we have only been able to obtain, in addition to 

 the German observations, some which have been made in Russia 

 and in the north of Italy. 



In the first part of the Philosophical Transactions for 1814 is 

 an excellent essay by your great mathematician Mr. Ivory, who 

 is also so much esteemed in this country ; it is entitled " On a 

 New Method of deducing a first Approximation to the Orbit of 

 a Comet." I had great ])icasure in observing the striking re- 

 semblance between this method and that which I myself pub- 

 liiihed some years ago, and wliich has since that time been much 

 used on the Continent; and the coincidence was the more in- 

 teresting, as Mr. Ivory obtained the same solution, from his al- 

 gebraical invcitigation, which I had deduced from a more geo- 

 metrical consideration of the problem. My method may easily 

 have escaped Mr. Ivory's notice, as it was for a long time only 

 to be found in German publication.s : at present he will have 

 foiir.d it in Delambre's Astronomy, and perhaps also he may be 

 acquainted with the new and ver^ convenient form which Pro- 

 fessor Gauss has given to it in the Gottingen Transactions. I 

 8:!nd with this letter two copies of my little work ; one 1 beg you 

 to honour with a place in your library, the other to transmit to 

 Mr. Ivory, with the assurance of my particular respect. 



I am very desirous of being informed if Troughton's new circle 

 at Greenwich, with which Mr. Pond now m.akcs his observations, 

 is situated very near to Bird's quadrant, with which the principal 



part 



