V . -^ 



^^Tt-T— 1 n,— ^-.^. •. 



f 



/ 



17 



6 



M A T H E M A T I C A L and 



only caufed the limb of the Sun to tremble and undulate, 

 but gave it, as it were, the form of a large faw, the emi- 

 nences being luminous, and the cavities black, which 

 fhifted places like a tempeftuous ocean." Thefe things 

 made it difficult to fix even the time of the external contad 

 to greater certainty than 5 or 6 feconds; but, at the inter- 

 nal contad:, he found difficulties of another kind. For 

 *' when he thought Venus ought to be entirely within the 

 Sun, the luminous cufps did not join immediately behind 

 her; but on the contrary, fhe feemed to carry the limb of 

 the Sun along with her, which appeared to bend towards 

 her, leaving a black cavity in his limb; and the body of 

 the planet, though he thought he faw it all within the Sun, 

 ftill fliot out a black column or ligament towards his limb." 

 It was intended to have compared all the other Ameri- 

 can obfervations (as well as thofe of Norriton and Phila- 

 delphia,) with the European obfervations, for deducing 

 the Sun's parallax; but I could only find leifure to make 

 the calculations for two places more, viz the Capes of Dela- 

 ware, and Bafkenridge, New-Jcrfey. Mr. Biddle\ exter- 

 nal contad: at tlic Capes, compared with the ten places a- 

 bove, gives 9^^254 for the Sun's parallax on the tranfit 

 day; and dcdudling 8''^ of time, by which he thinks he 

 noted his internal contact too late, on account of the tre- 

 mulous motion on the Sun's limb, occafioned by the denfe 



vapors from the fca, that contad gives 8^',862. The ex- 

 ternal contad (obfervcd at Baflcenridge, by Lord Stirling) 



gives, on a like comparifon y^JS^'^ ^^^ ^^^ internal con- 

 tad 8^I668. 



His Lordlliip has not yet had an opportunity to afcertain 

 the longitude of Raflcenridgc with the neceifary precifion; 

 and the contains by Mr. Biddle being about \6" later, than 

 they ought to be from his difference of longitude (allowing 

 for parallax) compared with Philadelphia and Norriton; he 

 apprehends that the time of his clock could not be depend- 

 ed on nearer than to about one quarter ot a minute, hav- 

 ing only a very fmall equal altitude inflrument mounted 



on 





J 

 f 



. 



^ 





\ 



■<S 



