42 MATHEMATICAL and^ 



As the Society were pleafed to appoint Jqfeph Shippeny 

 Elq. Dr. Hugh Williamfon^ Mr. Charles ThomfoUy Mr.- Tho^ 

 mas Prior^ and myfelj^ as a committee to obferve the tran- 

 fit at the obfervatoryy which they had erected in this city, 

 we fpared neither time nor labour to have every thing ne- 

 cefTary for the obfervation in readinefs. We were provided 

 with an excellent fed:or of 6 feet radius^ made by the ac- 

 curate Mr. Bird, and an equal altitude and tranfit Lnftru- 

 ment, both belonging to the honourable Proprietaries of 

 this province, whicli the Governor very gcneroufly lent to 

 the fociety on this occafion. Our telefcopes were, a large 

 refledor of 4 feet focus and 7 inches aperture, which mag- 

 nified from 100 to 400 times with an excellent mi- 



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y 



which 



the affembly of the province had ordered over at the re- 

 queftof the fociety; a refracting telefcope of 24 feet focus 



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Mr 



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gether with another rcfledor of la inches focus. With 

 thefe, and a good time-piece, we promifed ourfelves the 

 pleafure of making accurate obfervations, if the wxather 

 fhould prove favourable. For this purpofe we met fre- 

 quently before the day of the tranfit, to adjuftour inftru- 

 ments, and to remove every local obftru£lion that might 



hinder our obfervations. 



Some of us gave particular attention to the regulation 

 of the time-piece, and therefore took the paflage of the 

 Sun's limbs over the crofs hairs of the tranfit inftrumcnt, 

 both forenoon and afternoon for many days before and 

 after the tranfit, and particularly on that day. As it had 

 three horizontal hairs fixed in the focus, it afforded us fix 

 fets of correfponding altitudes, which generally agreed in 

 giving the time of apparent noon within 2 feconds of each 

 other; fo that by comparing them together daily, and ap- 

 plying the proper equations for correfponding altitudesy 

 on account of the Sun's change of declination between the 



forenoon 



