208 REMAEKS ON THE SMALL PLANETS. 



Pandora, (1,683.18 days,) Pallas, (1,683.86,) and Loetitia, (1,684.8.) 

 These numbers, it should be added, are far from being definitive. 

 We have adopted the tables of M. Mtedler, who inscribes the names 

 of the calculators, besides the results they have obtained. Sliould a 

 different catalogue be preferred, that, for instance, of the Annuaire du 

 Bureau des Longitudes, these approximations might perhaps disappear, 

 but we should lind others quite as remarkable. It were to be wished, 

 on that account, that the attention of astronomers should be directed, 

 in preference, to those asteroids whose revolutions present, in point 

 of duration, but slight differences ; perhaps those differences will be 

 still further diminished by a more rigorous calculation of elements. 

 In any case, when their progression shall have brought into helio- 

 centric conjunction two planets, describing their orbits in the same 

 number of days, their prolonged proximity will compensate, no doubt, 

 for the feebleness of their masses, and there must result perturbations 

 of a singular nature — perhaps a libration, which will reduce their 

 mean years to a perfect identity. 



The synodal revolution of an asteroid is evidently so much the 

 longer as its mean movement is more rapid. Thus Flora or Ariana 

 come into opposition but nine times in thirteen years, while Euphro- 

 syne or Maximiliana do so nine times in eleven years. 



Eccentricities. — The orbits of the asteroids are, in general, much 

 more eccentric than those of the elder planets. The lowest eccen- 

 tricities (Concordia 0.040, Harmonia 0.046,) are three times greater 

 than those of the earth; the highest (Polymnia 0.338, Asia 0.320,) 

 are almost equal to that of the comet of Faye. On the whole, of the 

 70 orbits now known, 18 are more eccentric than the orbit of Mer- 

 cury, (0.2056,) 8 less so than the orbit of Mars, (0.096,) and the rest 

 are of intermediate eccentricities. Hence it results that if the small 

 planets have, like the great, a daily movement about an axis more or 

 less inclined to the plane of their orbits, the duration of seasons must 

 be there very unequal, and the temperature, for one of their hemis- 

 pheres, much more extreme than on the earth. Polymnia, for in- 

 stance, is twice as near the sun at its perihelion as at its aphelion ; 

 the heat and light, therefore, which fall on its entire surface vary in 

 the ratio of 4 to 1 : the apparent diameter of the sun is then 8' 27" 

 at its maximum and 4' 11" at its minimum, while, for the earth, the 

 extreme numbers differ by only y'o of their amount. From this it re- 

 sults that, if the equator of Polymnia is not very much inclined to its 

 orbit, the seasons there depend, above all, on the distances from the 

 sun, which circumstance determines winter or summer for all the 

 points of the planet at the same time. 



VII. 



DISTRIBUTION OP THE REMARKABLE POINTS OF THE ORBITS ON THE CELESTIAL 



SPHERE. 



It is suflficient to cast an eye on the columns in which are inscribed 

 the longitudes of the perihelia, or those of the ascending nodes, to 

 see that these longitudes are not distributed after a uniform manner 



