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ASTRONOMICAL PAPERS. 



1/7 



oil a theodolite, to regulate by, and the wind very high on 

 June 2d. In other refpeils, there cannot by the leaft doubt 

 of the accuracy of his obfervations, having an excellent te- 

 lefcope, and acknowledged abilities for the ufe of it; nor 

 can there be an uncertainty of fo much as 3'^of time in 

 the longitude of his obfervatory, in refped to the places 

 ^bovementioned. 



Neverthelefs, if the parallax: of the Sun deduced from 

 thefe two obfervations of the external contad, be joined 

 with thofe of Norriton and Philadelphia, and the mean of 

 all the four be taken, it will give 8'^4907 for the Sun's 

 parallax on the tranfit day, agreeing exceedingly near with 

 what was got before by the comparifon from the Philadel^ 

 phia and Norriton external contads, viz, 8 



There is one fmall nicety, which the extreme ftridnefs 

 of the modern aftronomy might have required to be taken^ 

 into the foregoing calculations; andwhich was not thought 

 of in time. In the hypochefis of the earth's being an ob- 

 late fpheroid, the true latitude of places is more fouth than 

 the apparent latitude, or that deduced from obfervations. 



Tluis, the calcul. were made with lat. 40°.. 9'. 31" for 



Norriton. 



But, on account of the fpheroidal 

 fif/ure of the earth, fubtrad,. 



o. 14 



38 



39' 54- SJ 



I 1 



Remanis the true latitude, that 

 fhould have been ufed in the 



calculation, 



In like manner the latitude for Greenwich Ihould be 

 51^ l4^ i9^inftcadof5i°. 28^37^ 



Moreover the horizontal parallax aflumed in the calcu- 

 lations, being to be confidered as the equatoreal parallax, 

 Ihould bear a fmall redudion like wife for different latitudes. 



With this redudion, therefore, both of latitude and pa- 

 rallax, the calculations for Greenwich and Norriton v/ere 

 repeated, and the Sun's parallax came out, for the external 



contad 8'',8o5, inftead of 8%87i5. The difference is fo 



fmall, 



