— -. 1^ - 



126 



MATHEMATICAL and 



foUowlnj^, tot^ether with his Lordfhip's obfervations of the comet, which are iafcrted below. 

 He writes that he had no opportunities of making any other obfervations refpeding the trufi/a 

 of Venus except the contatils, and that his clock was properly regulated. 



a. Ohfcrvathn of the- cont^Sis of the Ihnhs o/'VKNUS «m/ the SUN, June T,d, I769, made by 



JkTr. William Poole, at Wilmingioriy in Fmnjyl'uania^ 



Lat. * 3yO. 44'- 3''- N. Long. jh. i! > f. W. 

 ExtratSled from a letter to Mr. OimnBiddlc^ and communicated to the Society, Dec. aid: 1770. 



With a rcfraiflor of ,12 feet magnifying power about 50 times. 



Mr. Pooh thinks the external contad was fcvcral fcconds 



before the time marked in, the margin. 



J „ ,. J I'he internal contadl was taken juil as the Sun's light began 



30. %0-% lU Int. ditto. , ^^ iurround the planet; though bis limb wu;j not vliibk 



beyond the planet, till a fccond or two afterwards. 



^ 



Apparent Time, 

 ah. la'. 48"^ ift P'xt. cont. 

 1. 



To the AMERICAN PHILOSOPHICAL SociETY, held at 



Philadelphia yir/?r(5W2(?//V^ ufeful knovulcdge. 



GENTLEMEN, 



TAKE the liberty, of communicating to you an im- 



dfry 



W 



s double re- 



fieding quadrant, which I have difcovered about two years 

 ago, which may beof fervice to fuch as ufe that excellent in- 

 ftrument. The greateft inconveniencies arifing from the 

 former conftru£tion of it are owingtothebadnefsof the glaf- 

 fes, the planes not being ground parallel to each other, and to 

 its {landing in need of a new and careful adjuftment almoft; 

 every time it is ufed. Both thefe imperfedions, I appre- 

 hend, arethorovighly removed by the newconftrudion pro- 

 pofed. I have heard, that Mr. 

 ous mathematician of London had alfo made fome improve- 

 ment in that inftrument; but I had not heard it before 

 eighteen months had elapfed, after I had perfe£ted my de- 

 raonftration of it, and fpoke to the workman to conflruCt 



it accordingly. 



As the propofed alteration makes the inftrument capable 

 of affording a number of obfervations, the unavoidable er- 

 rors 



* Mr. Vmlc had no opportunity of afcertaining the latitude or longitude of Wihnington by 

 celcfHal obfervations, but tlicy arc both to be gotten with fidhcient exadnefsfrom Mr. Biddlc\ 

 meafuremetit between NeAV-Cafllc and the Philaddpbia obfervatory p. 87. From that mea- 

 furcment, we get Wilmington weft of Philadelphia obfervatory 6741I pe^chcs=23^ %%",% 

 diff. of meridianr., or I^ 34'',6 of time; and fouth of the fame 4732^ p«jrche3=l2^ J2",6 diff. 

 of latitude. Whence the latitude and longUudq of Wilmington in rcfpcc^ to Greenwich, i\\i 

 as above fct down. W. SUIT H. 



■Cr 



'^:^y. '^y^A ■ 



