ASTRONOMICAL PAPERS 



119 



b 



ever, as both were fixed by celeftial obfervations, and ex- 

 perienced men, the fraall difference ought perhaps to be 

 divided; and if a mean be taken to reconcile it with the 

 terreftrial meafure, the lat. of the fouth point of Philadel- 

 phia would be 39°- ^^^ • 4^" 5 ^^^^ that of Norriton 40''* 9' . 



43 



// 



Mr. Rittenhoufe had only Sijfo 



Mellrs. Mali 



xon were 





furniflied with a compleat aflronomical redor5and did their 

 work to fix the lines of two provinces, it may be thought 

 that their determination is moft to be relied on. Never- 

 thelefs, the whole difference of 'i^^^ in the celeftial arc is fo 

 inconfidcrable, as not to give 40 chains on the furface of 

 the Earth. 



All the refiik in the above work are got without any itw 



fible error, by pkiin trigonometry, as the dificrent arcs are 

 fo very fmalL In eftimating the length of a degree, to de- 

 duce the difference of latitude between the two obfervatpries, 

 the fpheroidal figure of the earth was taken into confide- 

 ration; and the degree ineafurcd by MefTrs. Mqjon and 

 Dixoth in mean latitude 39°- 12^ = 363771 feet, wasmade 

 the flandard, which being lengthened in the ratio of 59, 

 7866 to 59,8o35gave363874for a degreeof the meridian 

 in the inean latitude between Philadelphia and Norriton, 

 which is only 103 feet more than the deg. iji lat. 39"- 12', 

 and makes but a fraction of a fecond difference in the lati- 

 tude, fo that it might have been difregarded. With ref- 



pe£l to feconds of time in longitude, no fenfible difference 

 can be obtained in the fmall diftance of about 1 1 mile 

 whether we confider the earth as a fphcre of fpheroid. 



In bringing out the ^2" of time difF. of long, a degree 

 of the equator was taken In proportion to Mcffrs. Ma/on 

 and D/\Wsdeg. ofthemerld. in lat. 39'', 12, in the ratio 



s 



gave 365070 for a det^ree of the equator. 



'^fp 



By taking a de^ 

 grce of longitude as fixed at the middle point by Mr. Maf- 

 kelyne m \d<i, 38"- j' > ss'^y '^"d fliying as the cofine of 

 that lat. is to cofine of mean latitude between Philadel- 



phia 



r* 



\ 



^ 



