iio 



PHILOSOPHICAL TRANSACTIONS. 



[anno 1771. 



washing or bleaching linen, it ought first to be dissolved in pure water, and the 

 solution be allowed to stand for some time, till the reddish or brown earth has 

 all precipitated to the bottom, and then the pure liquor ought to be poured off, 

 and what remains at the bottom be thrown into a filter; for if this precaution is 

 not taken, the reddish earth is in danger of giving a slight brown or reddish 

 colour to the neutral salts, or to afi'ect the colour of the linen. 



Lin. The Quantity of the Suns Parallax, as Deduced from the Observations of 

 the Transit oj Fenus, June 3, 1769. By Tho. Homsby, M.^., Prof, of 

 Astron., Oxford, and F.R.S. p. 574. 



The uncertainty as to the quantity of the sun's parallax, deduced from the ob- 

 servations of the transit of Venus in 1761 (whether it arose from the 

 unfavourable position of the planet, so that a sufficient difl^erence of time in the 

 total duration of the transit was not, and indeed could not be, obtained 

 from observations made at different places; or from the disagreement of the 

 observations of different astronomers, which were to serve as terms of com- 

 parison) seems now to be entirely removed: and from the observations made in 

 distant parts by the astronomers of different nations, and especially from those 

 made under the patronage and direction of this society, the learned of the 

 present time may congratulate themselves on obtaining as accurate a determina- 

 tion of the sun's distance, as perhaps the nature of the subject will admit. 



The two following tables give not only the observations themselves, but also 

 the computed differences of time from which the parallax was deduced. 



TABLE I. 

 Places. Latitude. Oberver'sNames. im.Cont. atlng. Int.Cont.atEgr. Obs. Durat. 



Wardhus 

 Kola 



Hudson's Bay 



California 



K. George's 1 

 Island / 



70° 25' 36"n 

 68 52 50 



58 4.7 32 



23 3 37 



17 28 55 s 



F. Hell 



M. Rumonsky 



{M. Wales 

 M. Dymond 

 Abbe Chappe 

 ( Capt. Cook 

 } Mr. Green 

 ( Dr. Solander 



15" 27" 

 15 35 



24.'6 

 23 



7 45.5 

 7 48.5 

 5 54 50.3 



3 14 

 3 14 



13 

 3 



'33" 

 53 

 45 

 45 

 37 

 29 

 30 



14' 

 19 



24.2" 

 23.: 

 32.4 

 57.5- 

 7. 



t.21 



3.2/ 

 2.4 



..5J 



TABLE IL 



Observ. darat. Diff. of comp. durat. Diff. of observ. durat. 



C King George's Island 5''29"' 



\ Wardhus 5 53 



-^Kola |5 53 



i Hudson's Bay 5 45 



(.California 5 37 



{California 5 37 



Wardhus 5 53 



Kola 5 53 



Hudson's Bay 5 45 



r Hudson's Bay 5 45 



J Wardhus 5 53 



I Kola 5 53 

 Mean of all 



52'.i 

 14 



\9 



23.7 



32.4 



32.4 



14 



19 



23.7 



23.7 



14 



19 



23"' 



23 



15 



7 



15 

 16 



8 



7 

 7 



3r.36" 



41 .09 

 51.90 



42 .43 



48.93 

 4.41 

 9.47 



39.46 

 49.19 



23°" 21'.5 



23 26 .5 



15 31 .2 



7 29.9 



15 



15 

 8 



7 

 7 



51 .6 



56.6 



1 .3 



50 3 

 55.3 



Sun's parallax. 



^jq 



8".639 

 8 .611 

 8 .511 

 8 .46 i 



8 .724 

 8 .629 

 8 .555 



8 .905 

 8 .813 

 8 .650 



