ON TWO CELESTIAL BODIES. 123 



inches, would be feen under an angle of 2' 28 ,, ,7 ; three quar- Excellent refult 

 ters of which are l'5l",52. This quantity, divided by the ° Q „ 2 * r "' aiam * 

 power 516,54, gives 0'',2159, or, as we have given it 

 abridged, 0",22. 



13 h 7'. I removed the micrometer to the greatefl conve- 

 nient diftance, namely, 2136 inches, and compared Dr. 

 Olbers's ftar, which, on account of its great altitude, I faw 

 now in high perfection, with the lucid difk. It was, even at 

 this diftance, lefs than the diameter of the difk, in the propor- 

 tion of 2 to 3. 



When, by long continued attention, the appearance of Pallas 

 was reduced to its fmalleft fize, I judged it to bear no greater 

 proportion to the diameter of the lucid difk of the micrometer, 

 than as 1 to 2. 



In confequence of thefe meafures, it appears that the dia-Diam. of Pallas 

 meter of Pallas, according to the firfl of them, is 0'',17 ; and, ° ,I3 ' 

 according to the laft, where the greatefl poffible difttnftnefs 

 was obtained, only 0", 13. 



If it fhould appear almoft incredible that thefe curious ob- Proof by the 

 jeds could give fo fmall an image, had they been fo much jjjjj^jjj^ 

 magnified as has been reported, I can fay, that curiofity led of the telefcopc 

 me to throw the piclure of Jupiter, given by the fame tele- ^ as j™ 1 ? as heA * 

 fcopeand magnifying power, on a wall at the diftance of 1318 

 inches, of which it covered a fpace that meaiured 12 feet H 

 inches. I do not mention this as a meafure of Jupiter, for the 

 wall was not perfectly at right angles to the telefcope, on which 

 account the projected image would be a little larger than it 

 fhould have been, nor was I very attentive to other necefTary 

 minute circumfrances, which would be required for an accu- 

 rate meafure ; but we fee at once, from the fize of this picture, 

 that the power of the telefcope exerted itfelf to the full of what 

 has been flated. 



As we generally can judge befl of comparative magnitudes, Rough compa- 



when the meafures are, as it were, brought home to us : it will tatlon o{ tnc <*»*- 



• r i . 'i £. • i meters of thefe 



not be amits to reduce them to miles. This, however, cannot bodies in miles : 



be done with great precifion, till we are more perfectly ac- 

 quainted with the elements of the orbits of thefe flars. But, for 

 our prefent purpofe, it will befufficiently accurate, if we admit 

 their mean diftances from the fun, as the moft recent informa- 

 tion at prefent ftates them ; for Ceres 2,6024; and for Pallas 

 2,3. The geocentric longitudes and north latitudes, at the time 



of 





