£00 ON COMETS. 



General con- J n this table the reader may perceive, 

 fusions. ■_, , . .' 



1. 1 hat, during the last eighteen years, observations on 



comets have been more frequent than ever; and that 

 the vigilance of astronomers to discover new ones has 

 equalled that they have employed in discovering also new 

 planets. 

 Perihelion dis- 2. That, of the comets observed, those which in their pe- 

 rihelion have approached the sun neaier than the Earth's 

 mean distance from it are double the number of those, the 

 perihelion of which exceeds this distance. Four of them 

 have approached nearer to the sun than the tenth of the 

 Earth's mean distance, and four others nearly within one 

 fifth of it. 

 Direction. 3. That, with regard to the direction of their motion, 



twelve have been retrograde, and nine direct. 

 Longitude of ^ That, as to the longitude of their ascending node, and 

 the node and „,.-'.«.,. . •••,.«. , , ~ , 



perihelion. of their perihelion, it answers indifferently to the 360 degrees 



of the circle, on which that longitude is reckoned. 

 Difference be- Nothing in the solar system is more remarkable, than the 

 and planets. S indeterminateness of the places of the orbits of comets, of 

 their inclination in all angles to the plane of the ecliptic, of 

 their eccentricities, of the place of their perihelion, and of 

 the direction of their movement, if compared with the pre- 

 cise determinations to which the planets are subjected. The 

 orbits of the latter are nearly circular, and very little in- 

 clined to the plane of the ecliptic : all the planets, both pri- 

 mary and secondary, move in the same direction, from west 

 to east ; and those, the rotation of which we have been able 

 to observe, turn on their axis in the same direction. Thus 

 Not owing to *^ e planetary system, says Mr. Laplace, in his Systtme du 

 chance. Monde, displays to us forty-two movements in this direction, 



and it is four millions of millions to one, that this arrange- 

 ment was not the effect of chance. Different final causes 

 therefore must have presided over the different formation 

 and destination of the planets and comets. 



VIII. 



